Fix check_run events using subject instead of repo extension

The github-events trampoline sets event.SetSubject(repoFullName) which
becomes ce-subject attribute, but does NOT set a 'repo' extension.

- Change extension_key from 'repo' to 'subject' for check-run-workqueue
- Rename parseRepoURL to parseRepoKey to handle both URL and subject formats
- Add tests for subject format (owner/repo)

This allows check_run completion events to flow through the workqueue
and trigger CI fixer reconciliation.

driftlessaf/cmd/pr-reconciler/main.go

@@ -292,6 +292,9 @@ var prURLRegex = regexp.MustCompile(`^https://github\.com/([^/]+)/([^/]+)/pull/(
 // repoURLRegex matches GitHub repo URLs like https://github.com/owner/repo
 var repoURLRegex = regexp.MustCompile(`^https://github\.com/([^/]+)/([^/]+)$`)
 
+// repoSubjectRegex matches repo subject format like owner/repo (from CloudEvents subject)
+var repoSubjectRegex = regexp.MustCompile(`^([^/]+)/([^/]+)$`)
+
 // ciState represents the evaluated state of CI checks
 type ciState int
 
@@ -357,12 +360,21 @@ func parsePRURL(url string) (owner, repo string, number int, err error) {
 	return matches[1], matches[2], number, nil
 }
 
-func parseRepoURL(url string) (owner, repo string, err error) {
-	matches := repoURLRegex.FindStringSubmatch(url)
-	if matches == nil {
-		return "", "", fmt.Errorf("invalid repo URL: %s", url)
+// parseRepoKey parses a repo identifier which can be either:
+// - Full URL: https://github.com/owner/repo
+// - Subject format: owner/repo (from CloudEvents subject attribute)
+func parseRepoKey(key string) (owner, repo string, err error) {
+	// Try full URL format first
+	matches := repoURLRegex.FindStringSubmatch(key)
+	if matches != nil {
+		return matches[1], matches[2], nil
 	}
-	return matches[1], matches[2], nil
+	// Try subject format (owner/repo)
+	matches = repoSubjectRegex.FindStringSubmatch(key)
+	if matches != nil {
+		return matches[1], matches[2], nil
+	}
+	return "", "", fmt.Errorf("invalid repo key: %s", key)
 }
 
 func (r *PRReconciler) Process(ctx context.Context, req *workqueue.ProcessRequest) (*workqueue.ProcessResponse, error) {
@@ -372,7 +384,7 @@ func (r *PRReconciler) Process(ctx context.Context, req *workqueue.ProcessReques
 	if err != nil {
 		// Key is not a PR URL - might be a repo URL from check_run events.
 		// Try to parse as repo URL and handle check_run completion.
-		owner, repo, parseErr := parseRepoURL(req.Key)
+		owner, repo, parseErr := parseRepoKey(req.Key)
 		if parseErr != nil {
 			log.Warnf("skipping unknown key format: %v", err)
 			return &workqueue.ProcessResponse{}, nil

driftlessaf/cmd/pr-reconciler/main_test.go

@@ -314,34 +314,48 @@ func TestParsePRURL(t *testing.T) {
 	}
 }
 
-func TestParseRepoURL(t *testing.T) {
+func TestParseRepoKey(t *testing.T) {
 	for _, tt := range []struct {
 		desc      string
-		url       string
+		key       string
 		wantOwner string
 		wantRepo  string
 		wantErr   bool
 	}{{
 		desc:      "valid repo URL",
-		url:       "https://github.com/owner/repo",
+		key:       "https://github.com/owner/repo",
 		wantOwner: "owner",
 		wantRepo:  "repo",
 	}, {
 		desc:      "valid repo URL with dashes",
-		url:       "https://github.com/my-org/my-repo",
+		key:       "https://github.com/my-org/my-repo",
 		wantOwner: "my-org",
 		wantRepo:  "my-repo",
 	}, {
-		desc:    "PR URL is not a repo URL",
-		url:     "https://github.com/owner/repo/pull/123",
+		desc:      "subject format owner/repo",
+		key:       "owner/repo",
+		wantOwner: "owner",
+		wantRepo:  "repo",
+	}, {
+		desc:      "subject format with dashes",
+		key:       "my-org/my-repo",
+		wantOwner: "my-org",
+		wantRepo:  "my-repo",
+	}, {
+		desc:    "PR URL is not a repo key",
+		key:     "https://github.com/owner/repo/pull/123",
 		wantErr: true,
 	}, {
 		desc:    "empty string",
-		url:     "",
+		key:     "",
+		wantErr: true,
+	}, {
+		desc:    "just owner no repo",
+		key:     "owner",
 		wantErr: true,
 	}} {
 		t.Run(tt.desc, func(t *testing.T) {
-			owner, repo, err := parseRepoURL(tt.url)
+			owner, repo, err := parseRepoKey(tt.key)
 			if tt.wantErr {
 				if err == nil {
 					t.Errorf("expected error, got owner=%q repo=%q", owner, repo)

driftlessaf/trigger.tf

@@ -47,8 +47,10 @@ module "check-run-workqueue" {
     "action" = "completed"
   }]
 
-  # Use repository URL as the key since check_run events don't have pullrequesturl
-  extension_key = "repo"
+  # Use subject (repo full name like "owner/repo") as the key.
+  # The trampoline sets event.SetSubject(repoFullName) which becomes ce-subject attribute.
+  # Note: "repo" extension doesn't exist - the trampoline only sets subject, not a repo extension.
+  extension_key = "subject"
 
   workqueue = {
     name = module.pr-reconciler.receiver.name