fix: persist respawnEnabled state to state.json

The respawn controller's enabled/disabled state was not being saved,
so CLI status couldn't show whether respawn was active.

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

src/types.ts

@@ -74,6 +74,8 @@ export interface SessionState {
   inputTokens?: number;
   /** Output tokens used */
   outputTokens?: number;
+  /** Whether respawn controller is currently enabled/running */
+  respawnEnabled?: boolean;
   /** Respawn controller config (if enabled) */
   respawnConfig?: RespawnConfig & { durationMinutes?: number };
   /** Ralph / Todo tracker enabled */