missions: phase_runner — actually execute mission phases

Root-cause fix for "we hit launch, waited overnight, nothing ran."
mission_orchestrator materialized teams + agents fine, but nothing
enqueued the actual work — mission_phases stayed 'pending' forever
and topology_runs count for the mission was 0.

New crates/cm-api/src/phase_runner.rs — background worker on 10s
poll that does three things:

  1. start_pending_phases — for every mission_phase with
     status='pending' AND parent mission.status='running' AND all
     lower-order phases already 'completed', enqueue one
     topology_runs row per team whose (mission_id, purpose) matches
     the phase kind:
       phase=research → teams with purpose='research'
       phase=coding   → teams with purpose='coding'
       phase=benchmark → teams with purpose='coding' (fallback)
       phase=security_scan → teams with purpose 'security' | 'coding'
     Each run gets a phase-kind-specific task text combining the
     mission title/description + a directive for that phase.
     Flips phase to 'running' after enqueue.
  2. close_finished_phases — SQL sweep that flips phases whose
     topology_runs are all terminal to 'completed' (or 'failed' if
     any run failed).
  3. close_finished_missions — same shape for missions whose phases
     are all terminal.

Spawned alongside task_card_worker in clawmates-server main.rs.

Ordering enforced by mission_phases.order_idx — a coding phase
doesn't fire until its research phase completes.

Idempotent: every state transition is guarded so double-firing on a
race is safe. When a mission has no matching teams for a phase (bad
wizard state), the phase stays pending and the runner logs a skip
rather than getting stuck in a fail loop.

Existing topology_worker picks up the queued runs and drives them
through the ZeroClaw executor as usual.

crates/bins/clawmates-server/src/main.rs

@@ -288,6 +288,7 @@ async fn run() -> Result<(), String> {
     // for INT-XX markers in event payloads and upserts mission_tasks
     // rows so the canvas renders a live status timeline.
     cm_api::task_card_worker::spawn(pool.clone());
+    cm_api::phase_runner::spawn(pool.clone());
     // PDF renderer worker (Slice 6): watches mission_artifacts for
     // MD entries with render_pdf_status='pending', calls the
     // configured LLM (default Gemini 2.5 Flash) for styled HTML,