Trigger Retrospective

Manually enqueue a project orchestrator retrospective.

Creates a new project_retrospective and fires the worker. Returns scheduled=False (retrospective_id=None) when an active run already covers the project — the partial-unique gate dedupes concurrent triggers.

An explicit manual trigger passes force=True to bypass the deploy-dark gate (retro_agent_enabled) — that gate only suppresses the AUTO triggers. Tools still honour dry-run mode, so a manual run stays non-mutating while retro_agent_dry_run is on.