fix: skip commentBody validation for Forgejo review comment events

Forgejo's pull_request_review_comment payload doesn't include the
comment body. The Forgejo data fetcher retrieves it via REST instead.
Skip the COMMENT_BODY required check on Forgejo to avoid crashing.

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

src/create-prompt/index.ts

@@ -178,7 +178,9 @@ export function prepareContext(
           "IS_PR must be true for pull_request_review_comment event",
         );
       }
-      if (!commentBody) {
+      // Forgejo's pull_request_review_comment payload lacks the comment body;
+      // the Forgejo data fetcher retrieves it via REST instead.
+      if (!commentBody && detectPlatform() !== "forgejo") {
         throw new Error(
           "COMMENT_BODY is required for pull_request_review_comment event",
         );
@@ -188,7 +190,7 @@ export function prepareContext(
         isPR: true,
         prNumber,
         ...(commentId && { commentId }),
-        commentBody,
+        commentBody: commentBody || "",
         ...(claudeBranch && { claudeBranch }),
         ...(baseBranch && { baseBranch }),
       };