fix(vfs): correct temp file lock state tracking

Replace counter-based lock tracking with actual lock type storage in
localTempFile. CheckReservedLock() now accurately reflects whether the
lock is at Reserved level or higher, rather than just checking if any
lock operation occurred.

Add TestLocalTempFileLocking to validate lock state transitions and
CheckReservedLock behavior.

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

Co-Authored-By: Claude <[email protected]>

Author: corylanou

vfs_lock_test.go

@@ -626,6 +626,53 @@ func TestVFS_TempFileDeleteOnClose(t *testing.T) {
 	}
 }
 
+func TestLocalTempFileLocking(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "local-temp-*")
+	if err != nil {
+		t.Fatalf("create temp: %v", err)
+	}
+	tf := newLocalTempFile(f, false, nil)
+	defer tf.Close()
+
+	assertReserved := func(want bool) {
+		t.Helper()
+		got, err := tf.CheckReservedLock()
+		if err != nil {
+			t.Fatalf("check reserved: %v", err)
+		}
+		if got != want {
+			t.Fatalf("reserved lock state mismatch: got %v want %v", got, want)
+		}
+	}
+
+	assertReserved(false)
+
+	if err := tf.Lock(sqlite3vfs.LockShared); err != nil {
+		t.Fatalf("lock shared: %v", err)
+	}
+	assertReserved(false)
+
+	if err := tf.Lock(sqlite3vfs.LockReserved); err != nil {
+		t.Fatalf("lock reserved: %v", err)
+	}
+	assertReserved(true)
+
+	if err := tf.Unlock(sqlite3vfs.LockShared); err != nil {
+		t.Fatalf("unlock shared: %v", err)
+	}
+	assertReserved(false)
+
+	if err := tf.Lock(sqlite3vfs.LockExclusive); err != nil {
+		t.Fatalf("lock exclusive: %v", err)
+	}
+	assertReserved(true)
+
+	if err := tf.Unlock(sqlite3vfs.LockNone); err != nil {
+		t.Fatalf("unlock none: %v", err)
+	}
+	assertReserved(false)
+}
+
 func TestVFS_DeleteIgnoresMissingTempFiles(t *testing.T) {
 	vfs := NewVFS(nil, slog.Default())
 

vfs_temp_file.go

@@ -16,7 +16,7 @@ import (
 type localTempFile struct {
 	f             *os.File
 	deleteOnClose bool
-	lockCount     int64
+	lockType      atomic.Int32
 	onClose       func()
 }
 
@@ -65,20 +65,17 @@ func (tf *localTempFile) Lock(elock sqlite3vfs.LockType) error {
 	if elock == sqlite3vfs.LockNone {
 		return nil
 	}
-	atomic.AddInt64(&tf.lockCount, 1)
+	tf.lockType.Store(int32(elock))
 	return nil
 }
 
 func (tf *localTempFile) Unlock(elock sqlite3vfs.LockType) error {
-	if elock == sqlite3vfs.LockNone {
-		return nil
-	}
-	atomic.AddInt64(&tf.lockCount, -1)
+	tf.lockType.Store(int32(elock))
 	return nil
 }
 
 func (tf *localTempFile) CheckReservedLock() (bool, error) {
-	return atomic.LoadInt64(&tf.lockCount) > 0, nil
+	return sqlite3vfs.LockType(tf.lockType.Load()) >= sqlite3vfs.LockReserved, nil
 }
 
 func (tf *localTempFile) SectorSize() int64 {