[austinjiann]

Fresh source rebuilds could stall after short detached stages, lose source-frame correspondence during cleaning, fail on fresh object coordinates or empty GPU caches, and freeze browser playback when a PCM soundtrack was embedded in MOV. This change fixes those paths while retaining bounded provider permits, original media, failed attempts, and unchanged quality thresholds.

• Carry the selected run's stage authorization and VLM request budget through new/resumed workers; advance after short detached steps without overriding operator holds.
• Preserve exact tracked source samples through cleaning, retain decoder errors, and support bounded mask corrections without resetting shared attempt counts.
• Stage pinned object dependencies deliberately, fail offline before GPU work when incomplete, and package fresh object tracks using an explicitly labelled stature prior.
• Deliver H.264/PCM inputs as packet-identical MP4 plus sample-identical WAV; validate local delivery hashes and preserve changed/authored audio before any rebuild deletion.
• Keep rejected scale-fit reports and images with the run, and show currently running stages above retained failures in the admin.
• Compare generated front-center depth with source depth once per supported image texel. Counting every in-frustum splat incorrectly penalized hidden rear geometry and made the fit depend on hidden-splat density. Legacy statistics remain available; coverage counts and explicit approximation limits accompany the corrected measurement. Visible near/far errors still fail the same thresholds.

Validation: 1,317 Python tests passed locally, including 22 new visibility regressions; five production-CLI synthetic fixtures, Ruff, repository formatting, and independent diff review passed. Prior local checks passed 283 viewer unit tests, six admin tests, and the production viewer build. Actual in-app browser checks confirmed both fresh 120-frame avatars, three bottle throws, final-frame visibility, sound-enabled playback, pause/seek, and loop wrap through the normal scene endpoint. All four CI jobs passed on commit 6d12151.

The fresh rebuild is not a full E2E quality pass. The original run reached 15/19 stages before the generated room and scale-fit checks failed. One explicitly approved image-conditioned replacement restored the open landing, using 1,580 World Labs credits, but source-matched beginning/middle/end views still show missing interior stairs and an invented raised wedge. The corrected scale check also remains failed; placement, anchors, and accepted final verification have not advanced. Original assets and failure evidence are preserved. Media, credentials, generated outputs, and local evidence are excluded from this PR.

Independent code reviews were completed. The Bugbot-specific review tool was unavailable; no Bugbot pass is claimed.