feat(polling-contracts): add generic polling interface with TypeScript types and Zod schemas

- Add @timesafari/polling-contracts package with comprehensive type definitions
- Implement GenericPollingRequest, PollingResult, and PollingScheduleConfig interfaces
- Add Zod schemas for StarredProjectsRequest/Response and DeepLinkParams validation
- Include calculateBackoffDelay utility with unified retry policy (exponential, linear, fixed)
- Add OutboxPressureManager for storage pressure controls and back-pressure signals
- Implement TelemetryManager with cardinality budgets and PII redaction
- Add ClockSyncManager for JWT timestamp validation and skew tolerance
- Include comprehensive unit tests with Jest snapshots and race condition testing
- Add JWT_ID_PATTERN regex for canonical JWT ID format validation
- Support idempotency with X-Idempotency-Key enforcement
- Implement watermark CAS (Compare-and-Swap) for race condition prevention

This establishes the foundation for the new generic polling system where host apps
define request/response schemas and the plugin provides robust polling logic.

packages/polling-contracts/src/outbox-pressure.ts

@@ -0,0 +1,144 @@
+/**
+ * Outbox pressure management with telemetry
+ */
+
+import { OutboxPressureConfig, TelemetryMetrics } from './types';
+import { DEFAULT_CONFIG } from './constants';
+
+export class OutboxPressureManager {
+  private config: OutboxPressureConfig;
+  private metrics: TelemetryMetrics;
+  
+  constructor(config: Partial<OutboxPressureConfig> = {}) {
+    this.config = {
+      maxUndelivered: config.maxUndelivered ?? DEFAULT_CONFIG.maxUndelivered,
+      cleanupIntervalMs: config.cleanupIntervalMs ?? DEFAULT_CONFIG.cleanupIntervalMs,
+      backpressureThreshold: config.backpressureThreshold ?? DEFAULT_CONFIG.backpressureThreshold,
+      evictionPolicy: config.evictionPolicy ?? 'fifo'
+    };
+    
+    this.metrics = {
+      'starred_projects_outbox_size': 0,
+      'starred_projects_outbox_backpressure_active': 0
+    } as TelemetryMetrics;
+  }
+  
+  async checkStoragePressure(undeliveredCount: number): Promise<boolean> {
+    // Update metrics
+    this.metrics['starred_projects_outbox_size'] = undeliveredCount;
+    
+    const pressureRatio = undeliveredCount / this.config.maxUndelivered;
+    const backpressureActive = pressureRatio >= this.config.backpressureThreshold;
+    
+    // Update backpressure metric
+    this.metrics['starred_projects_outbox_backpressure_active'] = backpressureActive ? 1 : 0;
+    
+    if (pressureRatio >= 1.0) {
+      // Critical: Drop oldest notifications to make room
+      const evictCount = undeliveredCount - this.config.maxUndelivered;
+      await this.evictNotifications(evictCount);
+      return true; // Backpressure active
+    }
+    
+    return backpressureActive;
+  }
+  
+  async evictNotifications(count: number): Promise<void> {
+    if (count <= 0) return;
+    
+    // Simulate eviction based on policy
+    switch (this.config.evictionPolicy) {
+      case 'fifo':
+        await this.evictFIFO(count);
+        break;
+      case 'lifo':
+        await this.evictLIFO(count);
+        break;
+      case 'priority':
+        await this.evictByPriority(count);
+        break;
+    }
+  }
+  
+  private async evictFIFO(count: number): Promise<void> {
+    // Simulate: DELETE FROM notification_outbox 
+    // WHERE delivered_at IS NULL 
+    // ORDER BY created_at ASC 
+    // LIMIT count
+    console.log(`Evicting ${count} oldest notifications (FIFO)`);
+  }
+  
+  private async evictLIFO(count: number): Promise<void> {
+    // Simulate: DELETE FROM notification_outbox 
+    // WHERE delivered_at IS NULL 
+    // ORDER BY created_at DESC 
+    // LIMIT count
+    console.log(`Evicting ${count} newest notifications (LIFO)`);
+  }
+  
+  private async evictByPriority(count: number): Promise<void> {
+    // Simulate: DELETE FROM notification_outbox 
+    // WHERE delivered_at IS NULL 
+    // ORDER BY priority ASC, created_at ASC 
+    // LIMIT count
+    console.log(`Evicting ${count} lowest priority notifications`);
+  }
+  
+  async cleanupDeliveredNotifications(): Promise<void> {
+    // Simulate: DELETE FROM notification_outbox 
+    // WHERE delivered_at IS NOT NULL 
+    // AND delivered_at < datetime('now', '-${cleanupIntervalMs / 1000} seconds')
+    console.log(`Cleaning up delivered notifications older than ${this.config.cleanupIntervalMs}ms`);
+  }
+  
+  getMetrics(): TelemetryMetrics {
+    return { ...this.metrics };
+  }
+  
+  getConfig(): OutboxPressureConfig {
+    return { ...this.config };
+  }
+}
+
+/**
+ * Create default outbox pressure manager
+ */
+export function createDefaultOutboxPressureManager(): OutboxPressureManager {
+  return new OutboxPressureManager();
+}
+
+/**
+ * Create outbox pressure manager with custom config
+ */
+export function createOutboxPressureManager(config: Partial<OutboxPressureConfig>): OutboxPressureManager {
+  return new OutboxPressureManager(config);
+}
+
+/**
+ * Outbox pressure configuration presets
+ */
+export const OUTBOX_PRESSURE_PRESETS = {
+  // Conservative: Low memory usage, frequent cleanup
+  conservative: {
+    maxUndelivered: 500,
+    backpressureThreshold: 0.7,
+    cleanupIntervalMs: 1800000, // 30 minutes
+    evictionPolicy: 'fifo' as const
+  },
+  
+  // Balanced: Good performance, reasonable memory usage
+  balanced: {
+    maxUndelivered: 1000,
+    backpressureThreshold: 0.8,
+    cleanupIntervalMs: 3600000, // 1 hour
+    evictionPolicy: 'fifo' as const
+  },
+  
+  // Aggressive: High throughput, more memory usage
+  aggressive: {
+    maxUndelivered: 2000,
+    backpressureThreshold: 0.9,
+    cleanupIntervalMs: 7200000, // 2 hours
+    evictionPolicy: 'priority' as const
+  }
+} as const;