docs: consolidate screenshot provenance and release gates

[jlipworth]

Summary

Consolidates the still-relevant work from codex/store-demo-provenance (7f93e1ee) and codex/prerelease-disclosure-audit (a61eff14) onto current main (181b9431). No app runtime changes.

• Retain the public open-film/derived-artwork provenance snapshot and active capture/reviewer plan; distinguish fixture images from final store images.
• Recheck official Blender license pages and Apple screenshot size guidance on 2026-09-29. Preserve historical catalog/hash verification dates and require a fresh deployed-asset check before capture.
• Preserve merged fix: declare required-reason system uptime usage #328/docs: reconcile demo-service privacy and collection disclosures #329 privacy wording and archive-report gates rather than replaying stale text. Add the explicit Cold launch without connectivity blocks completed offline downloads #259 deferral and unchecked exact-candidate export/accessibility gates.
• Keep the original disclosure audit as dated evidence, with a subsequent-disposition note. Remove current-sounding simulator/worktree assumptions from the capture plan and add it to the active-plan index.
• Add a manifest consistency regression test; this verifies recorded metadata, not the remote asset bytes or legal clearance of eventual compositions.

Validation

• 10 screenshot tooling tests.
• Strict MkDocs, rendered/source links, Mermaid, repository redaction and tooling hygiene.
• Hermetic PMSKit tests (live probes excluded).
• Official source-page verification; no new film download or deployed-server checksum audit.

No simulator, live playback, infrastructure changes, account edits, uploads, version changes or physical-device acceptance. No final screenshots produced. No new native build required: docs/spec/test changes only.

Remaining scope

Related #92, #259, #280, #325, #326; this PR closes none of them. Final captures, storefront credits/editorial review, age suitability, exact-candidate reviewer journeys, signed-archive privacy reports and owner-approved account answers remain open. The source branches/worktrees are preserved until this consolidation is reviewed and merged; this PR does not remove them.