Fix daemon orphaning: track parent PID and exit when parent dies

- Add ParentPID field to DaemonLockInfo struct
- Daemon monitors parent process every 10 seconds
- Gracefully exits when parent process dies
- Prevents accumulation of orphaned daemons from dead sessions
- Fixes race conditions from multiple daemons on same database

Closes bd-zpnq

cmd/bd/daemon_parent_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+// TestDaemonExitsWhenParentDies verifies that the daemon exits when its parent process dies
+func TestDaemonExitsWhenParentDies(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping integration test in short mode")
+	}
+
+	t.Skip("Manual test - requires daemon to be run externally")
+	
+	// This is a manual test scenario:
+	// 1. Start a shell process that spawns the daemon
+	// 2. Verify daemon tracks parent PID
+	// 3. Kill the shell process
+	// 4. Verify daemon exits within 10-15 seconds
+	//
+	// To test manually:
+	//   $ sh -c 'bd daemon --interval 5s & sleep 100' &
+	//   $ SHELL_PID=$!
+	//   $ # Check daemon.lock has parent_pid set to SHELL_PID
+	//   $ kill $SHELL_PID
+	//   $ # Daemon should exit within 10-15 seconds
+}
+
+func mustAbs(t *testing.T, path string) string {
+	abs, err := filepath.Abs(path)
+	if err != nil {
+		t.Fatalf("Failed to get absolute path: %v", err)
+	}
+	return abs
+}
+
+func runGitCmd(t *testing.T, dir string, args ...string) {
+	cmd := exec.Command("git", args...)
+	cmd.Dir = dir
+	if err := cmd.Run(); err != nil {
+		t.Fatalf("git %v failed: %v", args, err)
+	}
+}