feat: add pagination metadata to gitea_list_prs (#340)

Return wrapped {prs, pagination} from gitea_list_prs with has_more,
inventory_complete, and page traversal via api_fetch_page. Route
gitea_review_pr inventory through gitea_list_prs so trust gates can
prove pagination finality. Add assess_list_prs_pagination_proof verifier.

Closes #340

gitea_auth.py

@@ -420,6 +420,43 @@ def api_get_all(url, auth_header, *, limit=None, page_size=50, max_pages=100,
     return results
 
 
+def api_fetch_page(url, auth_header, *, page=1, limit=50, **kwargs):
+    """Fetch one page from a Gitea list endpoint with explicit pagination metadata.
+
+    Returns ``(items, pagination)`` where *pagination* includes ``has_more``,
+    ``next_page``, and ``is_final_page`` derived from the returned page length.
+    """
+    page = max(1, int(page))
+    limit = max(1, min(50, int(limit)))
+    page_url = _add_query(url, page=page, limit=limit)
+    data = api_request("GET", page_url, auth_header, **kwargs)
+    if data is None:
+        pagination = {
+            "page": page,
+            "per_page": limit,
+            "returned_count": 0,
+            "has_more": False,
+            "next_page": None,
+            "is_final_page": True,
+        }
+        return [], pagination
+    if not isinstance(data, list):
+        raise RuntimeError(
+            f"expected a list page from Gitea, got {type(data).__name__}"
+        )
+    returned = len(data)
+    has_more = returned >= limit
+    pagination = {
+        "page": page,
+        "per_page": limit,
+        "returned_count": returned,
+        "has_more": has_more,
+        "next_page": page + 1 if has_more else None,
+        "is_final_page": not has_more,
+    }
+    return data, pagination
+
+
 def gitea_url(host, path):
     """Build a full URL for *host* and *path*, using http for loopback and https for others."""
     if not path.startswith("/"):