fix(#29 review r1): stack-delete leak, rollback/retention/version tests, UX trap

F3: deleting a file-based stack now removes the stack ROOT (compose/{id}) via a
new removeStackProjectDir helper, not stack.ProjectPath (which the PR repointed to
compose/{id}/v{N}) — old version dirs + parent no longer leak. Git stacks unchanged.
F1: tests for validateRollbackTarget (rejects 0/neg/>current/hole) and the rollback
snapshot (client content ignored, target read from disk, monotonic new version, note).
F2: tests for pruneStackFileVersionDirs (deletes given dirs, swallows errors) + the
post-commit gate contract + a monotonic-version regression guard.
F4: handler tests for ?version= (negative/out-of-range -> 400, valid version served,
legacy fallback).
F5: swagger @param version on GET file; @version 2.44.0 (handler.go) + package.json
2.44.0, matching APIVersion.
F6: the version selector no longer sets rollbackTo for the current/top version and
clears it on a manual buffer edit (so edits are honored, not silently discarded);
returning to the current version restores the current content. Distinguishes real
user edits from the programmatic version-load (CodeMirror ExternalChange).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

api/http/handler/stacks/stack_delete.go

@@ -139,13 +139,25 @@ func (handler *Handler) stackDelete(w http.ResponseWriter, r *http.Request) *htt
 		}
 	}
 
-	if err := handler.FileService.RemoveDirectory(stack.ProjectPath); err != nil {
+	if err := handler.removeStackProjectDir(stack); err != nil {
 		log.Warn().Err(err).Msg("Unable to remove stack files from disk")
 	}
 
 	return response.Empty(w)
 }
 
+// removeStackProjectDir deletes a stack's files from disk. For file-based (non-git) stacks the
+// whole stack root (compose/{id}) is removed so every versioned subfolder (v1..vN) is cleaned up,
+// because stack.ProjectPath only points at the current version directory (compose/{id}/v{N}).
+// Git stacks keep a ProjectPath of compose/{id}, so removing it directly preserves their behavior.
+func (handler *Handler) removeStackProjectDir(stack *portainer.Stack) error {
+	if stack.WorkflowID == 0 {
+		return handler.FileService.RemoveDirectory(handler.FileService.GetStackProjectPath(strconv.Itoa(int(stack.ID))))
+	}
+
+	return handler.FileService.RemoveDirectory(stack.ProjectPath)
+}
+
 func (handler *Handler) deleteExternalStack(r *http.Request, w http.ResponseWriter, stackName string, securityContext *security.RestrictedRequestContext) *httperror.HandlerError {
 	endpointID, err := request.RetrieveNumericQueryParameter(r, "endpointId", false)
 	if err != nil {
@@ -355,7 +367,7 @@ func (handler *Handler) stackDeleteKubernetesByName(w http.ResponseWriter, r *ht
 			continue
 		}
 
-		if err := handler.FileService.RemoveDirectory(stack.ProjectPath); err != nil {
+		if err := handler.removeStackProjectDir(&stack); err != nil {
 			errs = errors.Join(errs, err)
 			log.Warn().Err(err).Msg("Unable to remove stack files from disk")
 		}