feat(robomp): added incoming PR review feature with classify and submit

- Added `review_pr` task that checks out PR head in a detached worktree, classifies rank/type/area, and posts a batched GitHub review as `event=COMMENT`.
- Added four new host tools: `fetch_pr`, `classify_pr`, `pr_review_comment`, and `submit_pr_review`; review tools self-gate on `review_mode`, push/open-PR tools refuse when `review_mode` is set.
- Added sqlite staging table `pr_review_comments` with `stage_review_comment`, `list_staged_review_comments`, and `clear_staged_review_comments` DAOs.
- Routed `pull_request.opened/reopened/ready_for_review` to `review_pr` and extended `pull_request.closed` cleanup to any tracked PR regardless of author.

python/robomp/src/git_ops.py

@@ -439,6 +439,20 @@ def fetch_ref(repo_dir: Path, ref: str, *, token: str | None, safe_directory: Pa
         )
 
 
+def fetch_pr_head(
+    repo_dir: Path,
+    pr_number: int,
+    *,
+    token: str | None,
+    safe_directory: Path | None = None,
+) -> None:
+    """Fetch `refs/pull/<n>/head` into FETCH_HEAD for detached PR review worktrees."""
+    if pr_number <= 0:
+        raise ValueError(f"invalid PR number: {pr_number!r}")
+    args = ["fetch", "origin", f"pull/{pr_number}/head"]
+    _check(_run_git(args, cwd=repo_dir, token=token, safe_directory=safe_directory), ["git", *args])
+
+
 @dataclass(slots=True, frozen=True)
 class PushResult:
     head: str
@@ -646,6 +660,7 @@ __all__ = [
     "HeadDriftError",
     "PushResult",
     "clone",
+    "fetch_pr_head",
     "fetch_prune",
     "fetch_ref",
     "inspect_dirty_state",