feat: add local schedule cache + periodic sync to CalendarScheduler

- New ScheduleCache class: maintains today's full schedule locally
- CalendarBridgeClient.getDaySchedule(): fetch all slots for a date
- Scheduler now runs two intervals:
  - Heartbeat (60s): existing slot execution flow (unchanged)
  - Sync (5min): pulls full day schedule into local cache
- Exposes getScheduleCache() for tools and status reporting

This enables the plugin to detect slots assigned by other agents
between heartbeats and provides a complete local view of the schedule.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugin/calendar/scheduler.ts

@@ -19,6 +19,7 @@
 import { writeFileSync, readFileSync, existsSync, mkdirSync } from 'fs';
 import { join, dirname } from 'path';
 import { CalendarBridgeClient } from './calendar-bridge';
+import { ScheduleCache } from './schedule-cache';
 import {
   CalendarSlotResponse,
   SlotStatus,
@@ -44,6 +45,8 @@ export interface CalendarSchedulerConfig {
   };
   /** Heartbeat interval in milliseconds (default: 60000) */
   heartbeatIntervalMs?: number;
+  /** Schedule sync interval in milliseconds (default: 300000 = 5 min) */
+  syncIntervalMs?: number;
   /** Enable verbose debug logging */
   debug?: boolean;
   /** Directory for state persistence (default: plugin data dir) */
@@ -95,8 +98,10 @@ interface SchedulerState {
   currentSlot: CalendarSlotResponse | null;
   /** Last heartbeat timestamp */
   lastHeartbeatAt: Date | null;
-  /** Interval handle for cleanup */
+  /** Heartbeat interval handle */
   intervalHandle: ReturnType<typeof setInterval> | null;
+  /** Schedule sync interval handle */
+  syncIntervalHandle: ReturnType<typeof setInterval> | null;
   /** Set of slot IDs that have been deferred in current session */
   deferredSlotIds: Set<string>;
   /** Whether agent is currently processing a slot */
@@ -117,10 +122,13 @@ export class CalendarScheduler {
   private config: Required<CalendarSchedulerConfig>;
   private state: SchedulerState;
   private stateFilePath: string;
+  /** Local cache of today's full schedule, synced periodically from backend */
+  private scheduleCache: ScheduleCache = new ScheduleCache();
 
   constructor(config: CalendarSchedulerConfig) {
     this.config = {
       heartbeatIntervalMs: 60000, // 1 minute default
+      syncIntervalMs: 300_000,    // 5 minutes default
       debug: false,
       stateDir: this.getDefaultStateDir(),
       ...config,
@@ -133,6 +141,7 @@ export class CalendarScheduler {
       currentSlot: null,
       lastHeartbeatAt: null,
       intervalHandle: null,
+      syncIntervalHandle: null,
       deferredSlotIds: new Set(),
       isProcessing: false,
       isRestartPending: false,
@@ -327,14 +336,21 @@ export class CalendarScheduler {
     this.state.isRestartPending = false;
     this.config.logger.info('Calendar scheduler started');
 
-    // Run initial heartbeat immediately
+    // Run initial sync + heartbeat immediately
+    this.runSync();
     this.runHeartbeat();
 
-    // Schedule periodic heartbeats
+    // Schedule periodic heartbeats (slot execution checks)
     this.state.intervalHandle = setInterval(
       () => this.runHeartbeat(),
       this.config.heartbeatIntervalMs
     );
+
+    // Schedule periodic schedule sync (full day schedule refresh)
+    this.state.syncIntervalHandle = setInterval(
+      () => this.runSync(),
+      this.config.syncIntervalMs
+    );
   }
 
   /**
@@ -348,10 +364,41 @@ export class CalendarScheduler {
       clearInterval(this.state.intervalHandle);
       this.state.intervalHandle = null;
     }
+    if (this.state.syncIntervalHandle) {
+      clearInterval(this.state.syncIntervalHandle);
+      this.state.syncIntervalHandle = null;
+    }
 
     this.config.logger.info('Calendar scheduler stopped');
   }
 
+  /**
+   * Sync today's full schedule from backend into local cache.
+   * Runs every syncIntervalMs (default: 5 min).
+   * Catches new slots assigned by other agents or the manager.
+   */
+  async runSync(): Promise<void> {
+    if (!this.state.isRunning || this.state.isRestartPending) return;
+
+    const today = new Date().toISOString().slice(0, 10);
+    try {
+      const slots = await this.config.bridge.getDaySchedule(today);
+      if (slots) {
+        this.scheduleCache.sync(today, slots);
+        this.logDebug(`Schedule synced: ${slots.length} slots for ${today}`);
+      }
+    } catch (err) {
+      this.config.logger.warn(`Schedule sync failed: ${String(err)}`);
+    }
+  }
+
+  /**
+   * Get the local schedule cache (for status reporting / tools).
+   */
+  getScheduleCache(): ScheduleCache {
+    return this.scheduleCache;
+  }
+
   /**
    * Execute a single heartbeat cycle.
    * Fetches pending slots and handles execution logic.