fix: address medium severity issues from code review

- Fix inconsistent null handling in state-store (use ?? instead of ||)
- Add JSON.stringify error handling with specific messages
- Add error handling for SSE init event in app.js
- Fix spawn orchestrator silent failures (add logging)
- Fix statSync race condition in subagent-watcher
- Fix unbounded _taskNumberToContent Map in ralph-tracker
- Fix YAML pattern case sensitivity in ralph-config

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/web/public/app.js

@@ -985,7 +985,11 @@ class ClaudemanApp {
     };
 
     this.eventSource.addEventListener('init', (e) => {
-      this.handleInit(JSON.parse(e.data));
+      try {
+        this.handleInit(JSON.parse(e.data));
+      } catch (err) {
+        console.error('[SSE] Failed to parse init event:', err);
+      }
     });
 
     this.eventSource.addEventListener('session:created', (e) => {