fix(player/runtime): rebind timelines and bound paused seeks

[vanceingalls]

Part 3 of 3 in the HyperFrames caption convergence stack. Depends on #3472.

What changes

• Re-probes the same-origin direct timeline before player operations (legacy/fallback path).
• Reconciles the injected core runtime timeline after a runtime-data handler replaces it.
• Publishes the reconciled timeline and duration before runtime-data-applied, so an immediate seek cannot clamp against the initial timeline.
• Defers initial iframe navigation and option-driven reloads until the custom element is connected.
• Preserves runtime-bridge readiness across the iframe load that follows the runtime ready message.
• Adds an HTTP(S)-validated runtime-src override for pairing a branch-tip player with its matching branch-tip core in an authorized local rig; unsafe schemes fall back to the pinned CDN runtime.
• Preserves playhead/rate/visibility across timeline replacement, clears stale state on removal, and keeps runtime-data failures observable.

Why

Data-driven caption attach rebuilds the GSAP timeline. The direct player adapter and the injected runtime could retain the killed initial object, leaving playback on segment one. Real-browser validation exposed three additional ordering hazards: React can assign srcdoc before connection, the runtime ready message can precede iframe load, and a replacement could be acknowledged before its new duration was published.

Verification

• HyperFrames core: 124 test files / 2,542 tests passed; focused runtime tests, typecheck, build, oxlint, and oxfmt passed.

• Player: 12 test files / 360 tests passed; build, typecheck, oxlint, and oxfmt passed.

• Historical exact-browser proof against catalog 0.6.0 and the matching branch-tip core: create with React's srcdoc then runtime-src ordering; apply three segments; switch caption-highlight to caption-pill-karaoke; immediately seek to 0.2s, 1.7s, and 3.2s after each apply. Both styles reported duration 3.9s and landed all seeks exactly; the old player disconnected, the bridge stayed ready, and no runtime-data error fired.

• Current-head CI, Windows rendering, player performance, preview regression, CodeQL, and all nine regression shards are green.

Review size

390 additions and 9 deletions across 5 files, below the 1,500-line stack limit.

[vanceingalls]

@claude review

[vanceingalls]

@claude review

[vanceingalls]

Post-push verification update:

• CI, regression, and Windows render verification all passed on 587e392f0 (runs 32915077051, 32915077042, 32915077056).
• The earlier cancelled workflow rows are superseded-run history, not failures.
• Local core/player suites and retained-channel browser proof are documented in the PR body.

No code changes are pending; awaiting the fresh review approval.

[vanceingalls]

@claude review

Please review final head 1b7e265, especially pre-connect attribute ordering, bridge readiness across iframe load, and timeline publication before runtime-data-applied.

[vanceingalls]

CPU-stability update at c89f5d71c:

• The sandbox transport no longer calls full GSAP totalTime(...) on every animation frame while paused. It still seeks while playing, after an explicit paused seek/timeline replacement, and once after a manual gesture.
• Six-player isolated measurement: 5,004 paused totalTime calls in 2s before; 30 initialization calls followed by zero additional calls over 3s after (~99.4% fewer full seeks).
• Focused core runtime verification passes 94/94, runtime typecheck passes, and the loopback runtime was rebuilt from this exact head.
• No behavior-specific caption code was added; this fixes the reusable HyperFrames transport loop.

@claude review

[vanceingalls]

Final-head automation update for c89f5d71c:

• Main CI passed on attempt 3 of run 33004020080; attempts 1–2 only exceeded the checkout step's one-minute job timeout before the file-size script ran.
• Replacement nine-shard regression run 33004020095 passed.
• The inherited fix(player): report and fail closed on runtime delivery errors #3472 shard-8 timeout also passed on rerun 32944541371.
• gh pr checks now reports no failing or pending current check contexts. The old failed regression row in the raw rollup is superseded history.

The remaining gate is human review.