Record phase 6 measurements and compatibility verification

plans/phase6-report.md

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+# Phase 6 report
+
+Tested `4b1f520`, from Phase 5 `21c1273`. Adjacent-commit measurements isolate
+`5d6a154`: WebKit/LTE FCP 1032→1615 ms. Its selected classic CSS arrived late
+(1540–1711 ms); worker installation started after paint. Fonts matched their
+preloads. Default/force-cache and HTTP-cache handoff trials still transferred
+app.js twice.
+
+Shipped early classic style discovery (`e7a7cdc`), a single verified page-owned
+WebKit response and specific CSP hash (`a86fa1c`, refined through `9408ee0`),
+worker-owned stale-core contract protection (`97eb31e`), and native parser boot
+with low-priority app preloading (`4b1f520`). The loader shares the existing final
+core script; core contract 2 prevents unsafe old packing fallback. app.js,
+playback and sw-update.js are unchanged.
+
+Five-run final medians:
+
+| Engine/profile | Phase 5→6 FCP ms | Phase 5→6 cold bytes | app bodies |
+|---|---:|---:|---:|
+| WebKit/LTE | 1739→905 | 1097048→983326 | 2→1 |
+| WebKit/lossy | 4303→2748 | 1105402→990152 | 2→1 |
+| Chromium/LTE | 1356→1388 | 651012→653267 | 1→1 |
+| Chromium/lossy | 2052→1976 | 651096→653267 | 1→1 |
+
+WebKit paint, one-body and below-baseline wire targets pass (−16.6%/−16.1%
+versus original wire baseline). Phase 2 measured 1044/4045 ms over three runs.
+
+Strict zero regression is **not achieved**: Chrome/LTE FCP +32 ms, cold bytes
++0.35%, long tasks 278→304 ms; warm boots Chrome 410/403→418/442 and WebKit
+83/85→88/89 ms. Metadata adds ~0.4 KB per core update. Added loader/security
+work has a cost; complete timing attribution remains unproved. Contemporary
+Phase 5 controls and all offline/update deltas appear in
+[phase6-verification.md](phase6-verification.md), with actual command excerpts.
+Chromium cold boot improves 7043/11342→6478/10314 ms.
+
+Migration passes both engines with/without stalls; banner once, explicit legacy
+refresh, old URLs, N-1, offline and playback guards. Lazy/layout/feature seams,
+hidden timers, both rollback modes, 223 frontend/184 server/3 measurement tests
+pass. No fonts/icons re-downloaded. ASSET_HASHING=0 and ASSET_SYNC=0 remain.
+
+Real iPhone install/update, quota pressure and 30-minute locked-screen audio
+require owner checks. The historical fixture measures home launch, not autoplay.