feat(gitea): default-branch lru cache

Shared LRU avoids repeated Gitea calls for default-branch resolution;
the simple stdlib map alternative would race on concurrent access without
a mutex per entry, which is more code than the LRU.

internal/tools/file_read.go

@@ -57,11 +57,11 @@ func (t *FileRead) Call(ctx context.Context, raw json.RawMessage) (json.RawMessa
 
 	ref := args.Ref
 	if ref == "" {
-		repo, err := t.c.GetRepo(ctx, args.Owner, args.Name)
+		var err error
+		ref, err = t.c.DefaultBranch(ctx, args.Owner, args.Name)
 		if err != nil {
 			return nil, err
 		}
-		ref = repo.DefaultBranch
 	}
 
 	fc, err := t.c.GetFileContents(ctx, args.Owner, args.Name, args.Path, ref)

internal/tools/file_write_branch.go

@@ -75,11 +75,11 @@ func (t *FileWriteBranch) Call(ctx context.Context, raw json.RawMessage) (json.R
 	if !exists {
 		base := args.Base
 		if base == "" {
-			repo, err := t.c.GetRepo(ctx, args.Owner, args.Name)
+			var err error
+			base, err = t.c.DefaultBranch(ctx, args.Owner, args.Name)
 			if err != nil {
 				return nil, err
 			}
-			base = repo.DefaultBranch
 		}
 		if err := t.c.CreateBranch(ctx, args.Owner, args.Name, args.Branch, base); err != nil {
 			return nil, err

internal/tools/workflow_run_trigger.go

@@ -61,11 +61,11 @@ func (t *WorkflowRunTrigger) Call(ctx context.Context, raw json.RawMessage) (jso
 
 	ref := args.Ref
 	if ref == "" {
-		repo, err := t.c.GetRepo(ctx, args.Owner, args.Name)
+		var err error
+		ref, err = t.c.DefaultBranch(ctx, args.Owner, args.Name)
 		if err != nil {
 			return nil, err
 		}
-		ref = repo.DefaultBranch
 	}
 
 	result, err := t.c.DispatchWorkflow(ctx, args.Owner, args.Name, args.Workflow, gitea.DispatchWorkflowArgs{