fix(web): tolerant polling, objectURL cleanup, throttled pointermove

- home/detail video pollers no longer clearInterval on a single transient error
  (give up only after 10 consecutive failures), matching the agent page
- agent page creates preview objectURLs inside useEffect so each has a matching
  revoke under strict-mode double-invocation
- login pointermove throttled via rAF and skipped on coarse pointers
- source-analysis.html: changelog entry for this hardening pass

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/app/detail/page.tsx

@@ -116,11 +116,16 @@ export default function DetailPage() {
 
   useEffect(() => {
     if (!job || !runningVideo) return
+    let failures = 0
     const timer = window.setInterval(async () => {
       try {
         setJob(await getJob(job.id))
+        failures = 0
       } catch {
-        window.clearInterval(timer)
+        // one transient 5xx / network blip must not freeze progress forever;
+        // only give up after sustained failures
+        failures += 1
+        if (failures >= 10) window.clearInterval(timer)
       }
     }, 2600)
     return () => window.clearInterval(timer)