fix(eval): dataset item ids that survive a URL path

Items were keyed `{repo}#{pr}`, e.g. `netcracker/interview#29`. Both
characters break the UI's item route: the `/` in `owner/repo` splits into
extra path segments, and everything after the `#` is a fragment the browser
never sends. Items were created successfully and then 404'd when opened.

Ids are now `{owner}__{repo}__pr{n}`, which needs no percent-encoding. The
real repo and pr stay intact in `input`, so nothing downstream reads the id
back apart. Session ids elsewhere keep the `{repo}#{pr}` form — those are
never path segments and feedback_scores depends on that shape.

The 28 existing items were unusable and are regenerable from feedback.db;
they were deleted and recreated under the new ids.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pilot/eval_bootstrap.py

@@ -111,6 +111,20 @@ def ensure_score_configs() -> dict:
 # 2. Dataset from recorded reviews
 # ---------------------------------------------------------------------------
 
+def item_id(repo: str, pr) -> str:
+    """A dataset-item id that survives being put in a URL path.
+
+    The obvious `{repo}#{pr}` is unusable: the UI routes items as
+    `/datasets/{id}/items/{item_id}`, so the `/` in `owner/repo` splits into
+    extra path segments and everything after the `#` is a fragment the browser
+    never sends. The item is created fine and then 404s when opened.
+
+    Session ids elsewhere keep the `{repo}#{pr}` form — those are never path
+    segments, and `feedback_scores` depends on that shape.
+    """
+    return f"{repo.replace('/', '__')}__pr{pr}"
+
+
 def read_review_items(db_path: str) -> list[dict]:
     """One dataset item per (repo, pr) the reviewer has run on.
 
@@ -140,7 +154,7 @@ def read_review_items(db_path: str) -> list[dict]:
             ).fetchall()
             items.append(
                 {
-                    "id": f'{row["repo"]}#{row["pr"]}',
+                    "id": item_id(row["repo"], row["pr"]),
                     "input": {
                         "repo": row["repo"],
                         "pr": int(row["pr"]),