fix(refinery): avoid race condition in foreground mode

In foreground mode, skip the tmux session check since we are likely
running inside the session that background mode created. Only check
PID to avoid self-detection.

Fixes the issue where gt refinery start gastown --foreground would
detect its own tmux session as already running.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/refinery/manager.go

@@ -134,22 +134,17 @@ func (m *Manager) Start(foreground bool) error {
 		return err
 	}
 
-	// Check if already running via tmux session
 	t := tmux.NewTmux()
 	sessionID := m.sessionName()
-	running, _ := t.HasSession(sessionID)
-	if running {
-		return ErrAlreadyRunning
-	}
-
-	// Also check via PID for backwards compatibility
-	if ref.State == StateRunning && ref.PID > 0 && processExists(ref.PID) {
-		return ErrAlreadyRunning
-	}
 
 	if foreground {
+		// In foreground mode, we're likely running inside the tmux session
+		// that background mode created. Only check PID to avoid self-detection.
+		if ref.State == StateRunning && ref.PID > 0 && processExists(ref.PID) {
+			return ErrAlreadyRunning
+		}
+
 		// Running in foreground - update state and run the Go-based polling loop
-		// This is the legacy mode, kept for backwards compatibility
 		now := time.Now()
 		ref.State = StateRunning
 		ref.StartedAt = &now
@@ -163,6 +158,17 @@ func (m *Manager) Start(foreground bool) error {
 		return m.run(ref)
 	}
 
+	// Background mode: check if session already exists
+	running, _ := t.HasSession(sessionID)
+	if running {
+		return ErrAlreadyRunning
+	}
+
+	// Also check via PID for backwards compatibility
+	if ref.State == StateRunning && ref.PID > 0 && processExists(ref.PID) {
+		return ErrAlreadyRunning
+	}
+
 	// Background mode: spawn a Claude agent in a tmux session
 	// The Claude agent handles MR processing using git commands and beads