feat: disable Ralph/Todo tracker auto-enable by default

Ralph tracker no longer auto-enables on pattern detection. It must be
explicitly enabled per-session (via API) or globally via the new
`ralphEnabled` AppConfig setting. Adds GET/PUT /api/config endpoints
for runtime configuration. Spawn agent ralph enable is unchanged.

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

src/ralph-tracker.ts

@@ -310,7 +310,7 @@ export class RalphTracker extends EventEmitter {
   private _loopUpdatePending: boolean = false;
 
   /** When true, prevents auto-enable on pattern detection */
-  private _autoEnableDisabled: boolean = false;
+  private _autoEnableDisabled: boolean = true;
 
   /** Maps task numbers from "✔ Task #N" format to their content for status updates */
   private _taskNumberToContent: Map<number, string> = new Map();