Shared capsule drops a captured video when its poster failed, while gate and CLI report complete #61

Impact: when a video's MP4 was inlined but its poster failed, the local export passes the strict gate. The shared capsule has no video, because raw video is never uploaded and the shared copy depends on the poster. The uploaded HTML shows "Video unavailable", and the shared .md says Not captured: 1 video (no file or poster). The unattended CLI still returns complete: true, because runAutomatedShareCapture assesses the local model, not the uploaded one.

Where: sourcecapsule.user.js: applySharedMediaUrls (5532) and createShareLink (5552) build the uploaded copy. runAutomatedShareCapture (5741) sets complete: assessment.verdict === 'clean' from the pre-upload assessment.

Evidence: Node repro with a stubbed Worker:

local strict verdict: clean blockers: 0
uploaded files: [ 'content.html', 'content.md', 'manifest.json' ]
shared md Completeness: Status: INCOMPLETE. Not captured: 1 video (no file or poster).
shared html has <video: false
runAutomatedShareCapture complete (assessment of LOCAL model): true

Related to #9 (share link creation strips media from the live model), but a separate cause.

Environment: main 72777ef (v1.6.8). Engine loaded in Node through the module.exports guard, GM_xmlhttpRequest stubbed. No browser, no live Worker.

Next action: compute complete and warnings from the model that was actually uploaded. Alternatively, make "video bytes with no poster" a share-time blocker, so the owner learns the shared copy will lack it.