fix: route Forgejo review comment updates to issue comment API

On Forgejo, the tracking comment for pull_request_review_comment events
is always created as a regular issue comment (because Forgejo's webhook
payload lacks the top-level comment object). The MCP server was
incorrectly setting isPullRequestReviewComment=true based on the event
name, causing every update to try pulls.updateReviewComment first —
which 404'd and silently swallowed Claude's responses.

Three fixes:
- MCP server: detect Forgejo and always use issue comment path
- update-comment-link: skip pulls.getReviewComment on Forgejo (saves
  one wasted 404 API call)
- update-claude-comment: expand fallback to also catch 422 (defense
  in depth for Forgejo edge cases)

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

src/mcp/github-comment-server.ts

@@ -52,8 +52,18 @@ server.tool(
         baseUrl: GITHUB_API_URL,
       });
 
+      // The tracking comment is always created as a regular issue comment on
+      // Forgejo because Forgejo's pull_request_review_comment payload lacks the
+      // top-level `comment` object (so createInitialComment falls back to
+      // issues.createComment). On GitHub, the tracking comment IS a review
+      // comment reply (created via pulls.createReplyForReviewComment).
+      //
+      // Setting this wrong causes every MCP update to first try
+      // pulls.updateReviewComment (404), and if the fallback doesn't trigger,
+      // Claude's responses never reach the comment.
+      const isForgejo = (process.env.GITHUB_API_URL || "").includes("/api/v1");
       const isPullRequestReviewComment =
-        eventName === "pull_request_review_comment";
+        eventName === "pull_request_review_comment" && !isForgejo;
 
       const sanitizedBody = sanitizeContent(body);