fix: use expand=1 instead of quick_pull=1 in PR URL on Forgejo

The prompt template hardcoded quick_pull=1 (GitHub-specific) in the
"Create a PR" URL. On Forgejo, this parameter is ignored so the
compare page doesn't auto-expand the PR creation form. Forgejo uses
expand=1 for this purpose.

Since Claude writes the PR URL into the comment body, and
updateForgejoCommentBody() extracts it (prLinkFromContent) with
priority over the URL generated by update-comment-link.ts, the
prompt template is the correct place to fix this.

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

src/create-prompt/index.ts

@@ -601,7 +601,7 @@ ${
   eventData.claudeBranch
     ? `
 When done with changes, provide a PR link:
-[Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...${eventData.claudeBranch}?quick_pull=1&title=<url-encoded-title>&body=<url-encoded-body>)
+[Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...${eventData.claudeBranch}?${detectPlatform() === "forgejo" ? "expand=1" : "quick_pull=1"}&title=<url-encoded-title>&body=<url-encoded-body>)
 Use THREE dots (...) between branches. URL-encode all parameters.`
     : ""
 }
@@ -791,7 +791,7 @@ ${eventData.eventName === "issue_comment" || eventData.eventName === "pull_reque
       ${
         eventData.claudeBranch
           ? `- Provide a URL to create a PR manually in this format:
-        [Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...<branch-name>?quick_pull=1&title=<url-encoded-title>&body=<url-encoded-body>)
+        [Create a PR](${GITHUB_SERVER_URL}/${context.repository}/compare/${eventData.baseBranch}...<branch-name>?${detectPlatform() === "forgejo" ? "expand=1" : "quick_pull=1"}&title=<url-encoded-title>&body=<url-encoded-body>)
         - IMPORTANT: Use THREE dots (...) between branch names, not two (..)
           Example: ${GITHUB_SERVER_URL}/${context.repository}/compare/main...feature-branch (correct)
           NOT: ${GITHUB_SERVER_URL}/${context.repository}/compare/main..feature-branch (incorrect)