refactor: improve code quality with stricter TypeScript and memory leak prevention

- Add stricter TypeScript compiler flags (noUnusedLocals, noUnusedParameters,
  noImplicitReturns, noImplicitOverride, noFallthroughCasesInSwitch,
  allowUnreachableCode, allowUnusedLabels)
- Remove unused variables caught by stricter flags:
  - Remove unused `renameSession` destructuring in App.tsx
  - Remove unused `BG_GRAY` constant in DirectAttach.ts
  - Remove unused `INPUT_BATCH_INTERVAL` constant in useSessionManager.ts
- Add proper EventEmitter cleanup to RalphLoop:
  - Store bound event handlers for cleanup
  - Add cleanupEventHandlers() method
  - Add destroy() method for complete cleanup
  - Add destroyRalphLoop() singleton cleanup function
- Update ralph-loop tests to use destroy() instead of stop() to prevent
  MaxListenersExceededWarning

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

tsconfig.json

@@ -15,7 +15,14 @@
     "declarationMap": true,
     "sourceMap": true,
     "jsx": "react-jsx",
-    "jsxImportSource": "react"
+    "jsxImportSource": "react",
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noImplicitOverride": true,
+    "noFallthroughCasesInSwitch": true,
+    "allowUnreachableCode": false,
+    "allowUnusedLabels": false
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]