fix: Ralph Loop wizard screen creation and session idle detection

- Fix screen creation failing when using cpulimit/nice (env vars were passed
  as command args instead of shell variables)
- Fix session status never becoming 'idle' after startInteractive()
- Add automatic state file cleanup on startup (removes orphaned sessions)
- Add /api/cleanup-state endpoint for manual cleanup
- Make frontend session readiness check more robust (20 attempts, multiple checks)
- Add fallback to direct PTY write if writeViaScreen fails

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

src/state-store.ts

@@ -177,6 +177,32 @@ export class StateStore {
     this.save();
   }
 
+  /**
+   * Cleans up stale sessions from state that don't have corresponding active sessions.
+   * @param activeSessionIds - Set of currently active session IDs
+   * @returns Number of sessions cleaned up
+   */
+  cleanupStaleSessions(activeSessionIds: Set<string>): number {
+    const allSessionIds = Object.keys(this.state.sessions);
+    let cleanedCount = 0;
+
+    for (const sessionId of allSessionIds) {
+      if (!activeSessionIds.has(sessionId)) {
+        delete this.state.sessions[sessionId];
+        // Also clean up Ralph state for this session
+        this.ralphStates.delete(sessionId);
+        cleanedCount++;
+      }
+    }
+
+    if (cleanedCount > 0) {
+      console.log(`[StateStore] Cleaned up ${cleanedCount} stale session(s) from state`);
+      this.save();
+    }
+
+    return cleanedCount;
+  }
+
   /** Returns all task states keyed by task ID. */
   getTasks() {
     return this.state.tasks;