[Fix] Task messages appear delivered before their turn starts

[roomote-roomote]

​Opened on behalf of @daniel-lxs. Follow up by mentioning @roomote-roomote or in the web UI.

What changed

• Persist task queue lifecycle updates through the same runtime envelope path used for delivered prompts.
• Use the runtime's allocated monotonic timestamp for every queue update so same-millisecond mutations cannot overwrite one another.
• Keep queued messages out of the transcript until the harness emits the corresponding user_prompt at a turn boundary or during explicit steering.
• Add regression coverage for ordinary queued messages, automatic delivery after the active turn, explicit steering of a queued message, and history hydration from persisted queue state.

Why this change was made

PR #1349 made task-message steering explicit, but the existing queue updates were live-socket-only while delivered prompts were persisted. After reconnecting or hydrating history, the UI had no durable queued state and could only reconstruct delivered transcript events, collapsing the distinction between accepted and injected messages.

Impact

Non-steering messages remain visibly queued until the harness actually starts their model turn, including after rapid queue mutations and history reloads. Automatic turn-boundary delivery and explicit steering both clear the persisted queue state and add the message to chat history only when the delivered user_prompt is emitted. Existing native steering and fallback replay behavior are unchanged.

[roomote-community]

No new code issues found. See task

• Queue-update timestamps can collide, allowing a stale queue snapshot to overwrite durable history.

_{Reviewed 93211d7}