feat(conductor): task state machine — TIMED_OUT state and retriable steps

- Add 'timed_out' to flow_runs/flow_steps CHECK constraints
- Add retry_count and max_retries columns to flow_steps
- Add timeout detection in advanceInner loop (configurable FLOW_STEP_TIMEOUT_MS)
- Add retriable logic: re-dispatch on timeout if maxRetries > 0 and retryCount < maxRetries
- Add isRetriable() + shouldRetry() pure decision functions
- Add timed_out handling to reconcileResumeStep and reconcileRun
- Add 'timed_out' to ws-frames enum, publishStep status type

apps/coder/src/services/__tests__/flow-runner-decisions.test.ts

@@ -52,6 +52,7 @@ const emptyState = (over: Partial<SchedulerState> = {}): SchedulerState => ({
   skipped: new Set(),
   inFlight: new Set(),
   excluded: new Set(),
+  timedOut: new Set(),
   ...over,
 });