remove unnecessary changes from PR

- Revert update-comment-link.ts changes (agent mode doesn't use this)
- Revert create-initial.ts changes (agent mode doesn't create comments)
- Remove unused default-branch.ts file
- Revert install-mcp-server.ts changes (agent mode uses minimal MCP)

These files are only used by tag mode for entity-based events, not needed
for workflow_dispatch/schedule support via agent mode.

src/github/operations/comments/create-initial.ts

@@ -22,12 +22,6 @@ export async function createInitialComment(
 ) {
   const { owner, repo } = context.repository;
 
-  // Entity events should always have entityNumber
-  if (!context.entityNumber) {
-    throw new Error("createInitialComment requires an entityNumber");
-  }
-  const entityNumber = context.entityNumber;
-
   const jobRunLink = createJobRunLink(owner, repo, context.runId);
   const initialBody = createCommentBody(jobRunLink);
 
@@ -42,7 +36,7 @@ export async function createInitialComment(
       const comments = await octokit.rest.issues.listComments({
         owner,
         repo,
-        issue_number: entityNumber,
+        issue_number: context.entityNumber,
       });
       const existingComment = comments.data.find((comment) => {
         const idMatch = comment.user?.id === CLAUDE_APP_BOT_ID;
@@ -65,7 +59,7 @@ export async function createInitialComment(
         response = await octokit.rest.issues.createComment({
           owner,
           repo,
-          issue_number: entityNumber,
+          issue_number: context.entityNumber,
           body: initialBody,
         });
       }
@@ -74,7 +68,7 @@ export async function createInitialComment(
       response = await octokit.rest.pulls.createReplyForReviewComment({
         owner,
         repo,
-        pull_number: entityNumber,
+        pull_number: context.entityNumber,
         comment_id: context.payload.comment.id,
         body: initialBody,
       });
@@ -83,7 +77,7 @@ export async function createInitialComment(
       response = await octokit.rest.issues.createComment({
         owner,
         repo,
-        issue_number: entityNumber,
+        issue_number: context.entityNumber,
         body: initialBody,
       });
     }
@@ -101,7 +95,7 @@ export async function createInitialComment(
       const response = await octokit.rest.issues.createComment({
         owner,
         repo,
-        issue_number: entityNumber,
+        issue_number: context.entityNumber,
         body: initialBody,
       });