fix(ci): catch urllib.error.HTTPError in gate-check-v3 comment posting

HttpError (e.g. 403 from missing write:repository) was not caught,
causing the entire script to crash after the verdict was already
computed. Now wrapped in try/except — comment-posting failure is non-fatal
and logged as a warning; the result with verdict is still returned.

Fixes: #543
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tools/gate-check-v3/gate_check.py

@@ -498,21 +498,25 @@ def run(repo: str, pr_number: int, post_comment: bool = False) -> dict:
                 "Content-Type": "application/json",
                 "Accept": "application/json",
             }
-            # Check if a gate-check comment already exists to avoid spamming
-            existing = api_list(f"/repos/{owner}/{name}/issues/{pr_number}/comments")
-            our_comments = [c for c in existing if "[gate-check-v3]" in (c.get("body") or "")]
-            if our_comments:
-                # Update latest
-                comment_id = our_comments[-1]["id"]
-                url = f"{API_BASE}/repos/{owner}/{name}/issues/comments/{comment_id}"
-                req = urllib.request.Request(url, data=json.dumps({"body": comment_body}).encode(), headers=headers, method="PATCH")
-                with urllib.request.urlopen(req) as r:
-                    r.read()
-            else:
-                url = f"{API_BASE}/repos/{owner}/{name}/issues/{pr_number}/comments"
-                req = urllib.request.Request(url, data=json.dumps({"body": comment_body}).encode(), headers=headers, method="POST")
-                with urllib.request.urlopen(req) as r:
-                    r.read()
+            try:
+                # Check if a gate-check comment already exists to avoid spamming
+                existing = api_list(f"/repos/{owner}/{name}/issues/{pr_number}/comments")
+                our_comments = [c for c in existing if "[gate-check-v3]" in (c.get("body") or "")]
+                if our_comments:
+                    # Update latest
+                    comment_id = our_comments[-1]["id"]
+                    url = f"{API_BASE}/repos/{owner}/{name}/issues/comments/{comment_id}"
+                    req = urllib.request.Request(url, data=json.dumps({"body": comment_body}).encode(), headers=headers, method="PATCH")
+                    with urllib.request.urlopen(req) as r:
+                        r.read()
+                else:
+                    url = f"{API_BASE}/repos/{owner}/{name}/issues/{pr_number}/comments"
+                    req = urllib.request.Request(url, data=json.dumps({"body": comment_body}).encode(), headers=headers, method="POST")
+                    with urllib.request.urlopen(req) as r:
+                        r.read()
+            except urllib.error.HTTPError as e:
+                # Non-fatal: token may lack write:repository. Verdict is already computed.
+                print(f"Warning: could not post comment (HTTP {e.code}) — token may lack write:repository permission", file=sys.stderr)
 
         return result