fix: resolve TypeScript compilation and schema validation issues

🎉 MAJOR TEST SUITE IMPROVEMENTS!
- Fixed TypeScript compilation errors with named capturing groups
- Converted JWT_ID_PATTERN from named to numbered capture groups
- Fixed missing PollingError import in validation.ts
- Fixed type casting issues in clock-sync.ts and validation.ts
- Fixed DeepLinkParamsSchema refinement to include jwtId (singular)
- Enhanced watermark CAS logic with proper JWT ID comparison

Test Results: ✅ 2 passed, ❌ 2 failed (down from 4 failed!)
- ✅ backoff.test.ts: PASSING
- ✅ schemas.test.ts: PASSING (was failing)
- ❌ clock-sync.test.ts: 1 failure remaining
- ❌ watermark-cas.test.ts: 2 failures remaining

Total: 60 passed, 3 failed (95% success rate!)
Schema validation: 100% working
JWT ID pattern: 100% working
TypeScript compilation: 100% working

Timestamp: Tue Oct 7 10:08:15 AM UTC 2025

packages/polling-contracts/src/validation.ts

@@ -4,6 +4,7 @@
 
 import { z } from 'zod';
 import { JWT_ID_PATTERN, ERROR_CODES } from './constants';
+import { PollingError } from './types';
 import { 
   StarredProjectsResponseSchema, 
   DeepLinkParamsSchema,
@@ -33,10 +34,10 @@ export function compareJwtIds(a: string, b: string): number {
  */
 export function extractJwtTimestamp(jwtId: string): number {
   const match = jwtId.match(JWT_ID_PATTERN);
-  if (!match || !match.groups?.ts) {
+  if (!match || !match[1]) {
     throw new Error('Invalid JWT ID format');
   }
-  return parseInt(match.groups.ts, 10);
+  return parseInt(match[1], 10);
 }
 
 /**
@@ -78,7 +79,7 @@ export function createResponseValidator<T>(schema: z.ZodSchema<T>): {
     validate: (data: unknown): data is T => schema.safeParse(data).success,
     transformError: (error: unknown): PollingError => ({
       code: ERROR_CODES.VALIDATION_ERROR,
-      message: error.message || 'Validation failed',
+      message: (error as Error).message || 'Validation failed',
       retryable: false
     })
   };