bd-vcg5: Add daemon crash recovery with panic handler + socket cleanup

Improvements:
1. Added top-level panic recovery in runDaemonLoop
   - Captures stack trace and logs to daemon.log
   - Writes daemon-error file with crash details for user visibility
   - Cleans up PID file on panic
2. Replaced os.Exit calls with return statements where possible
   - Allows deferred cleanup to run (lock release, socket removal, etc)
   - Improves graceful shutdown on errors
3. Enhanced stopDaemon forced-kill path
   - Removes stale socket file after process.Kill()
   - Prevents socket artifacts from accumulating
4. Added integration tests for crash recovery

Closes bd-vcg5

cmd/bd/daemon_lifecycle.go

@@ -334,13 +334,28 @@ func stopDaemon(pidFile string) {
 		fmt.Println("Daemon stopped")
 		return
 	}
+	
+	// Determine if this is global or local daemon
+	isGlobal := strings.Contains(pidFile, filepath.Join(".beads", "daemon.lock"))
+	socketPath := getSocketPathForPID(pidFile, isGlobal)
+	
 	if err := process.Kill(); err != nil {
 		// Ignore "process already finished" errors
 		if !strings.Contains(err.Error(), "process already finished") {
 			fmt.Fprintf(os.Stderr, "Error killing process: %v\n", err)
 		}
 	}
+	
+	// Clean up stale artifacts after forced kill
 	_ = os.Remove(pidFile)
+	
+	// Also remove socket file if it exists
+	if _, err := os.Stat(socketPath); err == nil {
+		if err := os.Remove(socketPath); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: failed to remove stale socket: %v\n", err)
+		}
+	}
+	
 	fmt.Println("Daemon killed")
 }