feat(scheduler): add cron-style scheduled jobs (backend)

Adds a saved/named scheduling layer on top of Codeman's existing session
primitives. Distinct from the legacy run-now ScheduledRun concept.

- types/scheduler.ts: ScheduledJob + ScheduledJobRun
- state-store: persist scheduledJobs/scheduledJobRuns in ~/.codeman/state.json
- scheduler/scheduler-time.ts: pure once/interval/daily/weekly next-run math
- scheduler/scheduler-service.ts: CRUD, Run Now, due-checker tick, run history;
  reuses SessionPort (create -> start -> writeViaMux) for launches
- web/routes/scheduler-routes.ts: /api/scheduler/jobs CRUD + run + history
- web/schemas.ts: zod validation with schedule-type-aware refinements
- web/sse-events.ts: scheduler:* events
- server.ts: wire service into route context + 30s background tick loop
- test/scheduler-time.test.ts: 14 unit tests for next-run calculations

Phase 1 discovery recorded in SCHEDULER_DISCOVERY.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rp7JhmQXcYJhmxFMdZuuah

src/types/app-state.ts

@@ -23,6 +23,7 @@ import type { SessionState } from './session.js';
 import type { TaskState } from './task.js';
 import type { RalphLoopState } from './ralph.js';
 import type { RespawnConfig } from './respawn.js';
+import type { ScheduledJob, ScheduledJobRun } from './scheduler.js';
 
 // ========== Global Stats Types ==========
 
@@ -111,6 +112,10 @@ export interface AppState {
   tokenStats?: TokenStats;
   /** Orchestrator Loop state (phased plan execution) */
   orchestrator?: import('./orchestrator.js').OrchestratorPersistState;
+  /** Cron-style scheduled jobs, keyed by job ID. */
+  scheduledJobs?: Record<string, ScheduledJob>;
+  /** Scheduled job run history, keyed by run ID. */
+  scheduledJobRuns?: Record<string, ScheduledJobRun>;
 }
 
 // ========== Default Configuration ==========