refactor(vfs): consolidate temp file tests into vfs_test.go

Move all VFS unit tests from vfs_lock_test.go into vfs_test.go for
better organization alongside the integration tests. Inline the
localTempFile implementation directly in vfs.go using sync/atomic
for lock state tracking, removing the need for vfs_temp_file.go.

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

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

Author: corylanou

vfs.go

@@ -14,6 +14,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	lru "github.com/hashicorp/golang-lru/v2"
@@ -297,6 +298,82 @@ func openFlagToOSFlag(flag sqlite3vfs.OpenFlag) int {
 
 var errTempFileNotFound = fmt.Errorf("temp file not tracked")
 
+// localTempFile fulfills sqlite3vfs.File solely for SQLite temp & transient files.
+// These files stay on the local filesystem and optionally delete themselves
+// when SQLite closes them (DeleteOnClose flag).
+type localTempFile struct {
+	f             *os.File
+	deleteOnClose bool
+	lockType      atomic.Int32
+	onClose       func()
+}
+
+func newLocalTempFile(f *os.File, deleteOnClose bool, onClose func()) *localTempFile {
+	return &localTempFile{f: f, deleteOnClose: deleteOnClose, onClose: onClose}
+}
+
+func (tf *localTempFile) Close() error {
+	err := tf.f.Close()
+	if tf.deleteOnClose {
+		if removeErr := os.Remove(tf.f.Name()); removeErr != nil && !os.IsNotExist(removeErr) && err == nil {
+			err = removeErr
+		}
+	}
+	if tf.onClose != nil {
+		tf.onClose()
+	}
+	return err
+}
+
+func (tf *localTempFile) ReadAt(p []byte, off int64) (n int, err error) {
+	return tf.f.ReadAt(p, off)
+}
+
+func (tf *localTempFile) WriteAt(b []byte, off int64) (n int, err error) {
+	return tf.f.WriteAt(b, off)
+}
+
+func (tf *localTempFile) Truncate(size int64) error {
+	return tf.f.Truncate(size)
+}
+
+func (tf *localTempFile) Sync(flag sqlite3vfs.SyncType) error {
+	return tf.f.Sync()
+}
+
+func (tf *localTempFile) FileSize() (int64, error) {
+	info, err := tf.f.Stat()
+	if err != nil {
+		return 0, err
+	}
+	return info.Size(), nil
+}
+
+func (tf *localTempFile) Lock(elock sqlite3vfs.LockType) error {
+	if elock == sqlite3vfs.LockNone {
+		return nil
+	}
+	tf.lockType.Store(int32(elock))
+	return nil
+}
+
+func (tf *localTempFile) Unlock(elock sqlite3vfs.LockType) error {
+	tf.lockType.Store(int32(elock))
+	return nil
+}
+
+func (tf *localTempFile) CheckReservedLock() (bool, error) {
+	return sqlite3vfs.LockType(tf.lockType.Load()) >= sqlite3vfs.LockReserved, nil
+}
+
+func (tf *localTempFile) SectorSize() int64 {
+	return 0
+}
+
+func (tf *localTempFile) DeviceCharacteristics() sqlite3vfs.DeviceCharacteristic {
+	return 0
+}
+
 // VFSFile implements the SQLite VFS file interface.
 type VFSFile struct {
 	mu     sync.Mutex