## What
- enforce a finite, validated `meta/videos.json` contract shared by Plan v1 and Plan v2
- preserve authored finite ends and source-derived trim-aware ends; bound any still-open end at the validated composition end
- fail distributed planning when any declared video source did not extract instead of publishing a blank-capable plan
- make the v1 chunk reader reject malformed/null video timing before frame injection
- route deterministic video-source/metadata failures as non-retryable in AWS and GCP while retaining retries for transient extraction failures
## Why
An open-ended video whose remote source could not be resolved retained `Infinity` through planning. Plan v2 correctly rejected that value, while Plan v1 serialized it as `null`; the v1 frame lookup could then suppress injected frames and silently produce incorrect output.
The invariant belongs at the shared metadata boundary. Both protocols must receive identical finite timing, and unavailable sources must fail closed before plan publication.
## Test plan
- [x] producer distributed planning, metadata, v1 chunk boundary, Plan v2 conversion/materialization, and public exports
- [x] core runtime media semantics (authored slots, natural duration, looping, non-looping hold)
- [x] engine video extraction and frame lookup
- [x] AWS Lambda/CDK/SAM and GCP Cloud Run error normalization/retry classification
- [x] producer, core, engine, AWS, and GCP typechecks/builds
- [x] formatting, oxlint, tracked-artifact, fallow, and commit hooks
- [x] exact incident composition replayed through the AWS Lambda handler's Lambda-local path in a Lambda-like container; Plan v1 and Plan v2 both fail closed as `VIDEO_SOURCE_UNRENDERABLE` during planning, before plan publication
- [x] full PR CI, including all nine regression shards and Windows render/tests
No production flags or deployment/release workflows are changed.
James Russo
557d82b6a9