feat: DTC carousel — 5 real codes with AI diagnosis, auto/manual scroll

New DTCCarousel section (#cases) sits between Hero and Showcase, showing
five common OBD-II codes with their OBDX output:

  P0420 · Catalytic Converter (Civic) — Plan within 2 weeks · $400–650
  P0301 · Cyl 1 Misfire (Camry)       — Easy fix · $80–200
  P0171 · Lean Fuel (F-150)           — Easy fix · $80–220
  P0442 · EVAP Small Leak (Equinox)   — Easy fix · $5–120
  P0700 · Trans Fault (Grand Cherokee)— Urgent · $100 diag–$3,500 rebuild

Each slide has an INPUT card (DTC + vehicle + mileage, big monospaced code
colored by severity) and an OUTPUT card (plain-English diagnosis + severity
pill + cost / drivability / first-move triplet).

UX: 6s auto-advance with linear progress bar, pause on hover & touch, prev
/next arrows, 5 jump-to dots, reduced-motion aware, aria-current on dots.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/DTCCarousel.tsx

@@ -0,0 +1,311 @@
+import { motion, AnimatePresence } from "framer-motion";
+import {
+  ChevronLeft,
+  ChevronRight,
+  Car,
+  Clock,
+  Sparkles,
+} from "lucide-react";
+import { useState, useEffect, useRef } from "react";
+
+const CASES = [
+  {
+    dtc: "P0420",
+    title: "Catalytic Converter Efficiency",
+    vehicle: "2018 Honda Civic 1.5L Turbo",
+    mileage: "108,432 mi",
+    plainEnglish:
+      "Your catalytic converter is past its prime. Not urgent — you have 1–2 weeks — but past 80k miles on this engine it's almost expected.",
+    severity: "Plan within 2 weeks",
+    severityColor: "#F59E0B",
+    cost: "$400 – $650",
+    drivable: "Yes, safely 1–2 weeks",
+    action: "Independent mechanic is fine — no dealer needed.",
+  },
+  {
+    dtc: "P0301",
+    title: "Cylinder 1 Misfire",
+    vehicle: "2020 Toyota Camry 2.5L",
+    mileage: "64,100 mi",
+    plainEnglish:
+      "One of your 4 cylinders is firing inconsistently. Usually a spark plug or ignition coil on cylinder 1. Cheap to rule out before assuming anything bigger.",
+    severity: "Easy fix",
+    severityColor: "#10B981",
+    cost: "$80 – $200",
+    drivable: "Drive gently until fixed",
+    action: "Start with a $30 plug + 30 min labor. If it comes back, swap the coil.",
+  },
+  {
+    dtc: "P0171",
+    title: "Lean Fuel Condition (Bank 1)",
+    vehicle: "2015 Ford F-150 5.0L V8",
+    mileage: "108,204 mi",
+    plainEnglish:
+      "Engine is getting too much air or not enough fuel. Usually a vacuum leak, dirty MAF sensor, or weak fuel pump — in that order of likelihood.",
+    severity: "Easy fix",
+    severityColor: "#10B981",
+    cost: "$80 – $220",
+    drivable: "Yes, but expect worse MPG",
+    action: "Smoke test for a vacuum leak first (~$30 at any shop).",
+  },
+  {
+    dtc: "P0442",
+    title: "EVAP System Small Leak",
+    vehicle: "2019 Chevy Equinox 1.5L",
+    mileage: "72,800 mi",
+    plainEnglish:
+      "A small leak somewhere in your fuel vapor recovery system. 9 times out of 10 it's the gas cap — check whether it clicks when you tighten it.",
+    severity: "Easy fix",
+    severityColor: "#10B981",
+    cost: "$5 – $120",
+    drivable: "Yes, completely safe",
+    action: "Swap the gas cap first ($5). If it returns, check the purge hose.",
+  },
+  {
+    dtc: "P0700",
+    title: "Transmission Control System Fault",
+    vehicle: "2017 Jeep Grand Cherokee 3.6L",
+    mileage: "94,100 mi",
+    plainEnglish:
+      "Your transmission computer detected an internal fault. P0700 is only the trigger — the specific P07xx code it stored alongside is what you actually need to read next.",
+    severity: "Urgent — diagnose now",
+    severityColor: "#EF4444",
+    cost: "$100 diag – $3,500 rebuild",
+    drivable: "Drive to a shop, not daily",
+    action: "Don't DIY. Dealer or a transmission specialist. Fluid change first if never serviced.",
+  },
+];
+
+const AUTO_INTERVAL_MS = 6000;
+
+export default function DTCCarousel() {
+  const [idx, setIdx] = useState(0);
+  const [paused, setPaused] = useState(false);
+  const [direction, setDirection] = useState(1);
+  const reducedMotion = useRef<boolean>(false);
+
+  useEffect(() => {
+    const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
+    reducedMotion.current = mq.matches;
+  }, []);
+
+  useEffect(() => {
+    if (paused) return;
+    const timer = setInterval(() => {
+      setDirection(1);
+      setIdx((prev) => (prev + 1) % CASES.length);
+    }, AUTO_INTERVAL_MS);
+    return () => clearInterval(timer);
+  }, [paused]);
+
+  const current = CASES[idx];
+  const goTo = (next: number) => {
+    setDirection(next > idx ? 1 : -1);
+    setIdx((next + CASES.length) % CASES.length);
+  };
+  const goPrev = () => goTo(idx - 1);
+  const goNext = () => goTo(idx + 1);
+
+  return (
+    <section
+      id="cases"
+      className="px-4 md:px-6 lg:px-8 pb-8 md:pb-12 space-y-4 md:space-y-5"
+    >
+      {/* Header */}
+      <motion.div
+        initial={{ opacity: 0, y: 16 }}
+        whileInView={{ opacity: 1, y: 0 }}
+        viewport={{ once: true, margin: "-80px" }}
+        transition={{ duration: 0.5 }}
+        className="rounded-[28px] bg-white border border-black/5 p-8 md:p-12 text-center"
+      >
+        <span className="inline-flex items-center gap-1.5 px-3 py-1 rounded-full bg-[#2563EB]/10 text-[#2563EB] text-xs font-semibold tracking-wider mb-4">
+          REAL DTC LOOKUPS
+        </span>
+        <h2 className="text-4xl md:text-5xl lg:text-6xl font-extrabold tracking-tight text-[#1A1A1A] leading-[1.05]">
+          Five codes.
+          <br />
+          <span className="text-[#1A1A1A]/40">
+            Five plain-English answers.
+          </span>
+        </h2>
+        <p className="mt-4 text-base md:text-lg text-[#1A1A1A]/60 max-w-2xl mx-auto">
+          Type a DTC into OBDX. Here's exactly what you'd get back.
+        </p>
+      </motion.div>
+
+      {/* Carousel container */}
+      <motion.div
+        initial={{ opacity: 0, y: 16 }}
+        whileInView={{ opacity: 1, y: 0 }}
+        viewport={{ once: true, margin: "-60px" }}
+        transition={{ duration: 0.5 }}
+        className="rounded-[28px] bg-[#FAFAF7] border border-black/5 p-5 md:p-7 relative"
+        onMouseEnter={() => setPaused(true)}
+        onMouseLeave={() => setPaused(false)}
+        onTouchStart={() => setPaused(true)}
+      >
+        {/* Slide area */}
+        <div className="relative overflow-hidden">
+          <AnimatePresence mode="wait" custom={direction}>
+            <motion.div
+              key={idx}
+              custom={direction}
+              initial={{ opacity: 0, x: reducedMotion.current ? 0 : 30 * direction }}
+              animate={{ opacity: 1, x: 0 }}
+              exit={{ opacity: 0, x: reducedMotion.current ? 0 : -30 * direction }}
+              transition={{ duration: 0.4, ease: "easeOut" }}
+              className="grid grid-cols-1 md:grid-cols-12 gap-4 md:gap-5"
+            >
+              {/* INPUT card */}
+              <div className="md:col-span-5 rounded-[24px] bg-[#1A1A1A] text-white p-7 md:p-8 min-h-[340px] flex flex-col justify-between relative overflow-hidden">
+                <div className="flex items-center gap-1.5 text-[10px] font-mono text-white/40 tracking-widest">
+                  <ChevronRight size={12} /> INPUT
+                </div>
+                <div>
+                  <div
+                    className="font-mono text-6xl md:text-7xl font-extrabold tracking-tight leading-none"
+                    style={{ color: current.severityColor }}
+                  >
+                    {current.dtc}
+                  </div>
+                  <div className="mt-4 text-lg md:text-xl font-bold text-white leading-snug">
+                    {current.title}
+                  </div>
+                </div>
+                <div className="space-y-2 pt-5 border-t border-white/10">
+                  <div className="flex items-center gap-2 text-xs text-white/65">
+                    <Car size={12} /> {current.vehicle}
+                  </div>
+                  <div className="flex items-center gap-2 text-xs font-mono text-white/40">
+                    <Clock size={12} /> {current.mileage}
+                  </div>
+                </div>
+              </div>
+
+              {/* OUTPUT card */}
+              <div className="md:col-span-7 rounded-[24px] bg-white border border-black/5 p-7 md:p-8 min-h-[340px] flex flex-col gap-5">
+                <div className="flex items-center justify-between gap-2 flex-wrap">
+                  <div className="flex items-center gap-1.5 text-[10px] font-mono text-[#2563EB] tracking-widest">
+                    <Sparkles size={12} /> AI DIAGNOSIS
+                  </div>
+                  <span
+                    className="inline-flex items-center gap-1.5 px-2.5 py-1 rounded-full text-[10px] font-bold uppercase tracking-wide"
+                    style={{
+                      background: `${current.severityColor}1F`,
+                      color: current.severityColor,
+                    }}
+                  >
+                    <span
+                      className="w-1 h-1 rounded-full"
+                      style={{ background: current.severityColor }}
+                    />
+                    {current.severity}
+                  </span>
+                </div>
+
+                <p className="text-base md:text-lg text-[#1A1A1A]/85 italic leading-relaxed flex-1">
+                  “{current.plainEnglish}”
+                </p>
+
+                <div className="grid grid-cols-1 md:grid-cols-3 gap-4 pt-4 border-t border-black/5">
+                  <div>
+                    <div className="text-[10px] font-mono text-[#1A1A1A]/40 uppercase tracking-widest">
+                      Cost estimate
+                    </div>
+                    <div className="text-base md:text-lg font-bold text-[#1A1A1A] mt-1 tabular-nums">
+                      {current.cost}
+                    </div>
+                  </div>
+                  <div>
+                    <div className="text-[10px] font-mono text-[#1A1A1A]/40 uppercase tracking-widest">
+                      Can you drive?
+                    </div>
+                    <div className="text-sm font-semibold text-[#1A1A1A] mt-1">
+                      {current.drivable}
+                    </div>
+                  </div>
+                  <div>
+                    <div className="text-[10px] font-mono text-[#1A1A1A]/40 uppercase tracking-widest">
+                      First move
+                    </div>
+                    <div className="text-xs text-[#1A1A1A]/70 mt-1 leading-snug">
+                      {current.action}
+                    </div>
+                  </div>
+                </div>
+              </div>
+            </motion.div>
+          </AnimatePresence>
+        </div>
+
+        {/* Progress bar (auto-advance indicator) */}
+        <div className="mt-5 h-[3px] bg-[#1A1A1A]/5 rounded-full overflow-hidden">
+          <motion.div
+            key={`bar-${idx}-${paused ? "p" : "r"}`}
+            initial={{ width: "0%" }}
+            animate={{ width: paused ? "0%" : "100%" }}
+            transition={{ duration: paused ? 0 : AUTO_INTERVAL_MS / 1000, ease: "linear" }}
+            className="h-full bg-[#2563EB]"
+          />
+        </div>
+
+        {/* Controls row */}
+        <div className="mt-5 flex items-center justify-between flex-wrap gap-3">
+          <div className="flex items-center gap-2">
+            {CASES.map((c, i) => (
+              <button
+                key={c.dtc}
+                type="button"
+                onClick={() => goTo(i)}
+                className={`h-1.5 rounded-full transition-all ${
+                  i === idx
+                    ? "w-8 bg-[#1A1A1A]"
+                    : "w-1.5 bg-[#1A1A1A]/20 hover:bg-[#1A1A1A]/40"
+                }`}
+                aria-label={`Show example ${i + 1}: ${c.dtc}`}
+                aria-current={i === idx}
+              />
+            ))}
+          </div>
+
+          <div className="flex items-center gap-3">
+            <span className="text-[11px] font-mono text-[#1A1A1A]/40 tabular-nums">
+              {String(idx + 1).padStart(2, "0")}
+              <span className="text-[#1A1A1A]/20 mx-1">/</span>
+              {String(CASES.length).padStart(2, "0")}
+            </span>
+            <button
+              type="button"
+              onClick={goPrev}
+              className="w-10 h-10 rounded-full bg-white border border-black/10 text-[#1A1A1A] flex items-center justify-center hover:bg-[#1A1A1A] hover:text-white hover:border-[#1A1A1A] transition"
+              aria-label="Previous example"
+            >
+              <ChevronLeft size={18} />
+            </button>
+            <button
+              type="button"
+              onClick={goNext}
+              className="w-10 h-10 rounded-full bg-[#1A1A1A] text-white flex items-center justify-center hover:bg-[#2563EB] transition"
+              aria-label="Next example"
+            >
+              <ChevronRight size={18} />
+            </button>
+          </div>
+        </div>
+
+        {/* Status indicator */}
+        <div className="mt-3 flex items-center gap-2 text-[10px] font-mono text-[#1A1A1A]/30">
+          <span
+            className={`w-1.5 h-1.5 rounded-full ${
+              paused ? "bg-[#1A1A1A]/20" : "bg-[#10B981] animate-pulse"
+            }`}
+          />
+          {paused
+            ? "Paused — move mouse out to resume"
+            : `Auto-advancing every ${AUTO_INTERVAL_MS / 1000}s · hover to pause`}
+        </div>
+      </motion.div>
+    </section>
+  );
+}