Register instance_guard for copy and avoid recycled inodes

Why: CI rejected the new table as missing from the storage-migrate copy list, and the replacement test passed on filesystems that reused the deleted inode.
Evidence: SELF go test TestCopyOrderCoversAllFixtureTables and TestDatabaseReplacementRefusedBeforeOpen.
Impact: SQLite to PostgreSQL copy keeps the guard row. The replacement test burns inodes until the new file is distinct.
Refs: docs/recovery/u8-sqlite-instance-guard.md
Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/storage-migrate/main.go

@@ -295,6 +295,8 @@ var copyOrder = []string{
 	"login_keys",
 	// U1 I3：服务实例 DB 身份（无外键；迁移须保留以免目标库丢锚）
 	"agent_system_identity",
+	// U8：活动服务锁的库内标记（无外键；迁移须保留以免目标库丢掉锁根）
+	"instance_guard",
 }
 
 const controlDDL = `

internal/instanceguard/guard_test.go

@@ -75,9 +75,32 @@ func TestDatabaseReplacementRefusedBeforeOpen(t *testing.T) {
 	if err := os.Remove(db); err != nil {
 		t.Fatal(err)
 	}
-	if err := os.WriteFile(db, []byte("replaced"), 0o600); err != nil {
+	raw, err := os.ReadFile(db + ".lock")
+	if err != nil {
 		t.Fatal(err)
 	}
+	rec, err := parseRecord(string(raw))
+	if err != nil || rec == nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 16; i++ {
+		if err := os.WriteFile(db, []byte("replaced"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		_, ino, exists, err := statFile(db)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if exists && ino != rec.DBIno {
+			break
+		}
+		if err := os.Remove(db); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, "inode-burn-"+string(rune('a'+i))), []byte("x"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
 	lease, err := Acquire(dir)
 	if err != nil {
 		t.Fatal(err)