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/schemas.ts

@@ -59,8 +59,8 @@ export const DeepLinkParamsSchema = z.object({
   jwtId: z.string().regex(JWT_ID_PATTERN).optional(),
   shortlink: z.string().min(1).optional()
 }).refine(
-  (data) => data.jwtIds || data.projectId || data.shortlink,
-  'At least one of jwtIds, projectId, or shortlink must be provided'
+  (data) => data.jwtIds || data.jwtId || data.projectId || data.shortlink,
+  'At least one of jwtIds, jwtId, projectId, or shortlink must be provided'
 );
 
 // Error response schema