feat(lifecycle): immediate daemon notification via SIGUSR1

- daemon.go: Add SIGUSR1 handler to process lifecycle requests immediately
- handoff.go: Signal daemon after sending lifecycle mail to deacon/
- mail.go: Show message IDs in hook output for direct reading

Previously, gt handoff would wait up to 5 min for daemon heartbeat poll.
Now lifecycle requests are processed within milliseconds.

Closes gt-zut3

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

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

internal/cmd/handoff.go

@@ -6,7 +6,9 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"syscall"
 	"time"
 
 	"github.com/spf13/cobra"
@@ -111,6 +113,16 @@ func runHandoff(cmd *cobra.Command, args []string) error {
 	}
 	fmt.Printf("%s Sent %s request to %s\n", style.Bold.Render("✓"), action, manager)
 
+	// Signal daemon for immediate processing (if manager is deacon)
+	if manager == "deacon/" {
+		if err := signalDaemon(townRoot); err != nil {
+			// Non-fatal: daemon will eventually poll
+			fmt.Printf("%s Could not signal daemon (will poll): %v\n", style.Dim.Render("○"), err)
+		} else {
+			fmt.Printf("%s Signaled daemon for immediate processing\n", style.Bold.Render("✓"))
+		}
+	}
+
 	// Set requesting state
 	if err := setRequestingState(role, action, townRoot); err != nil {
 		fmt.Printf("Warning: failed to set state: %v\n", err)
@@ -357,3 +369,28 @@ func setRequestingState(role Role, action HandoffAction, townRoot string) error
 
 	return os.WriteFile(stateFile, data, 0644)
 }
+
+// signalDaemon sends SIGUSR1 to the daemon to trigger immediate lifecycle processing.
+func signalDaemon(townRoot string) error {
+	pidFile := filepath.Join(townRoot, "daemon", "daemon.pid")
+	data, err := os.ReadFile(pidFile)
+	if err != nil {
+		return fmt.Errorf("reading daemon PID: %w", err)
+	}
+
+	pid, err := strconv.Atoi(strings.TrimSpace(string(data)))
+	if err != nil {
+		return fmt.Errorf("parsing daemon PID: %w", err)
+	}
+
+	process, err := os.FindProcess(pid)
+	if err != nil {
+		return fmt.Errorf("finding daemon process: %w", err)
+	}
+
+	if err := process.Signal(syscall.SIGUSR1); err != nil {
+		return fmt.Errorf("signaling daemon: %w", err)
+	}
+
+	return nil
+}

internal/cmd/mail.go

@@ -597,7 +597,7 @@ func runMailCheck(cmd *cobra.Command, args []string) error {
 			messages, _ := mailbox.ListUnread()
 			var subjects []string
 			for _, msg := range messages {
-				subjects = append(subjects, fmt.Sprintf("- From %s: %s", msg.From, msg.Subject))
+				subjects = append(subjects, fmt.Sprintf("- %s from %s: %s", msg.ID, msg.From, msg.Subject))
 			}
 
 			fmt.Println("<system-reminder>")

internal/daemon/daemon.go

@@ -85,7 +85,7 @@ func (d *Daemon) Run() error {
 
 	// Handle signals
 	sigChan := make(chan os.Signal, 1)
-	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM, syscall.SIGUSR1)
 
 	// Heartbeat ticker
 	ticker := time.NewTicker(d.config.HeartbeatInterval)
@@ -103,8 +103,14 @@ func (d *Daemon) Run() error {
 			return d.shutdown(state)
 
 		case sig := <-sigChan:
+			if sig == syscall.SIGUSR1 {
+				// SIGUSR1: immediate lifecycle processing (from gt handoff)
+				d.logger.Println("Received SIGUSR1, processing lifecycle requests immediately")
+				d.processLifecycleRequests()
+			} else {
 				d.logger.Printf("Received signal %v, shutting down", sig)
 				return d.shutdown(state)
+			}
 
 		case <-ticker.C:
 			d.heartbeat(state)