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/web/ports/index.ts

@@ -13,3 +13,4 @@ export type { ConfigPort } from './config-port.js';
 export type { InfraPort, ScheduledRun } from './infra-port.js';
 export type { AuthPort } from './auth-port.js';
 export type { OrchestratorPort } from './orchestrator-port.js';
+export type { SchedulerPort } from './scheduler-port.js';

src/web/ports/scheduler-port.ts

@@ -0,0 +1,10 @@
+/**
+ * @fileoverview Scheduler port — exposes the cron-style SchedulerService to
+ * route handlers via the shared route context.
+ */
+
+import type { SchedulerService } from '../../scheduler/scheduler-service.js';
+
+export interface SchedulerPort {
+  readonly scheduler: SchedulerService;
+}