feat: gt mail send now sends tmux notification to recipients

- Add DisplayMessage/DisplayMessageDefault to tmux package for non-disruptive
  status line notifications
- Change mail send to always notify recipients (not just high priority)
- Use display-message instead of send-keys to avoid disrupting agent input
- Support notifications for mayor, polecat, and refinery sessions

Closes gt-7lt

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

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

internal/mail/router.go

@@ -56,10 +56,8 @@ func (r *Router) Send(msg *Message) error {
 		return fmt.Errorf("sending message: %w", err)
 	}
 
-	// Optionally notify if recipient is a polecat with active session
-	if isPolecat(msg.To) && msg.Priority == PriorityHigh {
-		r.notifyPolecat(msg)
-	}
+	// Always notify recipient if they have an active session
+	r.notifyRecipient(msg)
 
 	return nil
 }
@@ -69,43 +67,44 @@ func (r *Router) GetMailbox(address string) (*Mailbox, error) {
 	return NewMailboxFromAddress(address, r.workDir), nil
 }
 
-// notifyPolecat sends a notification to a polecat's tmux session.
-func (r *Router) notifyPolecat(msg *Message) error {
-	// Parse rig/polecat from address
-	parts := strings.SplitN(msg.To, "/", 2)
-	if len(parts) != 2 {
-		return nil
+// notifyRecipient sends a notification to a recipient's tmux session.
+// Uses display-message for non-disruptive notification.
+// Supports mayor/, rig/polecat, and rig/refinery addresses.
+func (r *Router) notifyRecipient(msg *Message) error {
+	sessionID := addressToSessionID(msg.To)
+	if sessionID == "" {
+		return nil // Unable to determine session ID
 	}
 
-	rig := parts[0]
-	polecat := parts[1]
-
-	// Generate session name (matches session.Manager)
-	sessionID := fmt.Sprintf("gt-%s-%s", rig, polecat)
-
 	// Check if session exists
 	hasSession, err := r.tmux.HasSession(sessionID)
 	if err != nil || !hasSession {
 		return nil // No active session, skip notification
 	}
 
-	// Inject notification
-	notification := fmt.Sprintf("[MAIL] %s", msg.Subject)
-	return r.tmux.SendKeys(sessionID, notification)
+	// Display notification in status line (non-disruptive)
+	notification := fmt.Sprintf("[MAIL] From %s: %s", msg.From, msg.Subject)
+	return r.tmux.DisplayMessageDefault(sessionID, notification)
 }
 
-// isPolecat checks if an address points to a polecat.
-func isPolecat(address string) bool {
-	// Not mayor, not refinery, has rig/name format
+// addressToSessionID converts a mail address to a tmux session ID.
+// Returns empty string if address format is not recognized.
+func addressToSessionID(address string) string {
+	// Mayor address: "mayor/" or "mayor"
 	if strings.HasPrefix(address, "mayor") {
-		return false
+		return "gt-mayor"
 	}
 
+	// Rig-based address: "rig/target"
 	parts := strings.SplitN(address, "/", 2)
-	if len(parts) != 2 {
-		return false
+	if len(parts) != 2 || parts[1] == "" {
+		return ""
 	}
 
+	rig := parts[0]
 	target := parts[1]
-	return target != "" && target != "refinery"
+
+	// Polecat: gt-rig-polecat
+	// Refinery: gt-rig-refinery (if refinery has its own session)
+	return fmt.Sprintf("gt-%s-%s", rig, target)
 }

internal/tmux/tmux.go

@@ -200,6 +200,21 @@ type SessionInfo struct {
 	Attached  bool
 }
 
+// DisplayMessage shows a message in the tmux status line.
+// This is non-disruptive - it doesn't interrupt the session's input.
+// Duration is specified in milliseconds.
+func (t *Tmux) DisplayMessage(session, message string, durationMs int) error {
+	// Set display time temporarily, show message, then restore
+	// Use -d flag for duration in tmux 2.9+
+	_, err := t.run("display-message", "-t", session, "-d", fmt.Sprintf("%d", durationMs), message)
+	return err
+}
+
+// DisplayMessageDefault shows a message with default duration (5 seconds).
+func (t *Tmux) DisplayMessageDefault(session, message string) error {
+	return t.DisplayMessage(session, message, 5000)
+}
+
 // GetSessionInfo returns detailed information about a session.
 func (t *Tmux) GetSessionInfo(name string) (*SessionInfo, error) {
 	format := "#{session_name}|#{session_windows}|#{session_created_string}|#{session_attached}"