fix: handle missing comment payload in Forgejo review comment events

Forgejo's pull_request_review_comment event does not include a
top-level `comment` object in the payload (it's undefined), causing
a crash: "undefined is not an object (evaluating 'context.payload.comment.body')".

- trigger.ts: On Forgejo, always trigger for pull_request_review_comment
  events since the workflow already gates on event name alone
- create-prompt/index.ts: Use optional chaining for comment fields,
  fall back to actor/empty values (data fetcher provides full data)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/create-prompt/index.ts

@@ -142,9 +142,13 @@ export function prepareContext(
     commentBody = context.payload.review.body ?? "";
     triggerUsername = context.payload.review.user.login;
   } else if (isPullRequestReviewCommentEvent(context)) {
-    commentId = context.payload.comment.id.toString();
-    commentBody = context.payload.comment.body;
-    triggerUsername = context.payload.comment.user.login;
+    // Forgejo's pull_request_review_comment payload may not include a
+    // top-level `comment` object.  Use optional chaining and fall back
+    // to actor/empty values — the data fetcher provides the full data.
+    commentId = (context.payload as any).comment?.id?.toString();
+    commentBody = (context.payload as any).comment?.body ?? "";
+    triggerUsername =
+      (context.payload as any).comment?.user?.login ?? context.actor;
   } else if (isIssuesEvent(context)) {
     triggerUsername = context.payload.issue.user.login;
   }