refactor(launcher): remove dead _auto_merge_pr (M-4)

_auto_merge_pr had zero callers (merge is handled by the deployer agent).
Removed the method; _ensure_pr (still used by the auto-advance path) is kept.

src/agents/launcher.py

@@ -703,47 +703,6 @@ class AgentLauncher:
             logger.error(f"Failed to create PR for {branch}: {e}")
             return None
 
-    def _auto_merge_pr(self, repo: str, branch: str, task_id: int, work_item_id: str):
-        import httpx
-        owner = settings.gitea_owner
-        headers = {"Authorization": f"token {settings.gitea_token}"}
-        base_url = f"{settings.gitea_url}/api/v1"
-        try:
-            resp = httpx.get(
-                f"{base_url}/repos/{owner}/{repo}/pulls",
-                params={"state": "open", "head": branch},
-                headers=headers, timeout=10
-            )
-            resp.raise_for_status()
-            prs = resp.json()
-            if not prs:
-                pr_number = self._ensure_pr(repo, branch, 0)
-                if not pr_number:
-                    return False
-            else:
-                pr_number = prs[0]["number"]
-            resp = httpx.post(
-                f"{base_url}/repos/{owner}/{repo}/pulls/{pr_number}/merge",
-                json={"Do": "merge"},
-                headers=headers, timeout=30
-            )
-            if resp.status_code in (200, 204):
-                logger.info(f"PR #{pr_number} merged for {branch}")
-                update_task_stage(task_id, "done")
-                notify_stage_change(task_id, "deploy", "done")
-                plane_notify_stage(work_item_id, "deploy", "done")
-                from ..notifications import send_telegram
-                send_telegram(f"\u2705 {work_item_id}: PR #{pr_number} merged! deploy -> done. Task complete.")
-                return True
-            else:
-                logger.error(f"Merge failed for PR #{pr_number}: {resp.status_code} {resp.text}")
-                from ..notifications import send_telegram
-                send_telegram(f"\u26a0\ufe0f {work_item_id}: Auto-merge failed (HTTP {resp.status_code}). Manual merge needed.")
-                return False
-        except Exception as e:
-            logger.error(f"Auto-merge failed for {branch}: {e}")
-            return False
-
     def _write_task_file(self, repo: str, branch: str, task_file: str, content: str):
         """Write task file directly into the task's worktree.