fix(windows): serialize claim operations

tools/tht/internal/safeio/claim_windows.go

@@ -4,10 +4,16 @@ package safeio
 
 import (
 	"path/filepath"
+	"sync"
 
 	"golang.org/x/sys/windows"
 )
 
+// Windows retained directory handles intentionally omit FILE_SHARE_DELETE. Serialize the
+// complete path-based claim operations within this process so one operation cannot exhaust
+// another's bounded external-contention retry while its validated parent handle is retained.
+var windowsPrivateClaimOperationMu sync.Mutex
+
 type windowsPrivateRegular struct {
 	parents *windowsParentHandles
 	handle  windows.Handle
@@ -48,6 +54,8 @@ func openWindowsPrivateRegular(path string, links uint32) (*windowsPrivateRegula
 }
 
 func claimCanonicalPrivateRegular(source, claim string) (claimed bool, resultErr error) {
+	windowsPrivateClaimOperationMu.Lock()
+	defer windowsPrivateClaimOperationMu.Unlock()
 	directory, sourceName, claimName, err := openWindowsPrivateClaimDirectory(source, claim)
 	if err != nil {
 		return false, ErrUnsafeFile
@@ -62,6 +70,8 @@ func claimCanonicalPrivateRegular(source, claim string) (claimed bool, resultErr
 }
 
 func readCanonicalPrivateClaim(source, claim string, maximum int64) (contents []byte, found bool, resultErr error) {
+	windowsPrivateClaimOperationMu.Lock()
+	defer windowsPrivateClaimOperationMu.Unlock()
 	directory, sourceName, claimName, err := openWindowsPrivateClaimDirectory(source, claim)
 	if err != nil {
 		return nil, false, ErrUnsafeFile
@@ -94,6 +104,8 @@ func openWindowsPrivateClaimDirectory(source, claim string) (PrivateDirectoryHan
 }
 
 func removeCanonicalPrivateClaim(source, claim string) (removed bool, resultErr error) {
+	windowsPrivateClaimOperationMu.Lock()
+	defer windowsPrivateClaimOperationMu.Unlock()
 	directory, sourceName, claimName, err := openWindowsPrivateClaimDirectory(source, claim)
 	if err != nil {
 		return false, ErrUnsafeFile