Refactor silent debugging to happy path error handling

- Replaced instances of silentDebug with happy_path_error__with_fallback across multiple files to improve error logging and handling.
- Updated the utility function to provide clearer semantics for error handling when expected values are missing.
- Introduced a script to find potential silent failures in the codebase that may need to be addressed with the new error handling approach.

src/hooks/summary-hook.ts

@@ -15,6 +15,7 @@ import { createHookResponse } from './hook-response.js';
 import { logger } from '../utils/logger.js';
 import { ensureWorkerRunning, getWorkerPort } from '../shared/worker-utils.js';
 import { HOOK_TIMEOUTS } from '../shared/hook-constants.js';
+import { happy_path_error__with_fallback } from '../utils/silent-debug.js';
 
 export interface StopInput {
   session_id: string;
@@ -143,8 +144,13 @@ async function summaryHook(input?: StopInput): Promise<void> {
   const port = getWorkerPort();
 
   // Extract last user AND assistant messages from transcript
-  const lastUserMessage = extractLastUserMessage(input.transcript_path || '');
-  const lastAssistantMessage = extractLastAssistantMessage(input.transcript_path || '');
+  const transcriptPath = happy_path_error__with_fallback(
+    'Missing transcript_path in Stop hook input',
+    { session_id },
+    input.transcript_path || ''
+  );
+  const lastUserMessage = extractLastUserMessage(transcriptPath);
+  const lastAssistantMessage = extractLastAssistantMessage(transcriptPath);
 
   logger.dataIn('HOOK', 'Stop: Requesting summary', {
     workerPort: port,