Post-Phase-66: native recording marks and cutting

[hotzenplotz5]

Scope

Bounded post-Phase-66 Recording workflow for native VDR editing marks and native VDR cutting. This does not start Phase 67.

Current branch includes:

• source/architecture audit for VDR-native marks and RecordingsHandler cutting semantics;
• first read-only SuiteBridge RMARKS vertical using current VDR Recording identity;
• bounded native frame/timecode payload and marks revision contract;
• contract tests.

Safety boundary

• VDR remains canonical marks/cutter authority.
• No proprietary marks database.
• No browser filesystem writes.
• No shell/direct custom cutter.
• No Recording mutation is enabled by the current first slice.
• Runtime acceptance is not yet claimed.

Next on this draft

Continue through Agent/Control-Plane read wiring, then add explicitly fenced native mark mutations and RecordingsHandler.Add(ruCut, ...), frontend integration, automated tests and real yaVDR acceptance.

[hotzenplotz5]

Slice 2C runtime root-cause / replacement candidate freeze

The previously frozen real-acceptance candidate 8f66b9ea4cc643038cdf940c7d295b8b59f38677 is no longer sufficient for Slice 2C acceptance. On the real yaVDR, activating the candidate-defined Backend Agent command/SuiteBridge configuration made every command synchronization fail closed with invalid_command_poll_payload; the current Agent lease remained healthy while command/provider advertisement stayed on the historical generation-103 native-probe snapshot. No NMARKS reached VDR and no new marks mutation or cut was executed during diagnosis.

Root cause: core/agent/src/BackendAgentCommandJson.cpp::parseTypes() did not admit vdr.recording.marks.modify, although the same candidate's production Agent adds that command after live SuiteBridge recording-marks capability discovery and serializes it in /api/agent/v1/commands/poll.

Smallest product fix: fc57934731451d86f9c28ac8cc9c0b3a22cb8e05 (fix(agent): accept recording marks command polls). It adds the Recording-Marks command constant to the poll allowlist and a regression roundtrip covering the production marks command/provider facts. No ownership, mutation, VDR marks semantics, cutting, or Phase-67 scope changed.

Replacement hosted CI: run 33992116837 — PASS. All six jobs green: docs-check, frontend-regression-test, fast-regression-test, make-test-audit, architecture-check, packaging-regression-test. The targeted fast regression and final daemon build both passed.

New exact real-acceptance candidate is frozen at:
fc57934731451d86f9c28ac8cc9c0b3a22cb8e05

PR remains Draft/open/unmerged. Recording-Marks ownership has not yet been activated on the yaVDR after this fix, and no further real marks mutation is authorized until renewed explicit approval after fresh read-only prechecks.