unseen: cursor pagination for advisory enumeration

The GitHub /advisories endpoint ignores the `page` query parameter: it
paginates with the Link header's rel="next" cursor. The page-number
pager re-fetched the same first 100 rows forever and never terminated,
so enumeration never completed and no draft converged (a run fetched
5137 "pip pages" holding only 100 unique advisories).

Surface the successful response headers from JSONTransport, and walk the
rel="next" cursor per ecosystem until it is absent. The ecosystem /
published>=2019 / bare-number cwes filters are preserved on the first
request. Journal keys stay ecosystem:n (now cursor-walk positions) with
the saved next URL for resume; journal_version 4 refuses older journals.

Live smoke via the production pager: 300 unique advisories pulled in 3
API calls, advancing past the first page. Offline: 170 unseen tests
pass, ruff clean.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

benchmarks/unseen/draft.py

@@ -219,7 +219,7 @@ def inputs(used, seed, known_empty, clones):
         "used_set_digest": digest({label: sorted(names) for label, names in used.sources.items()}),
         "known_empty": sorted(known_empty),
         "clone_limit_bytes": getattr(clones, "limit_bytes", 500 * 1024 * 1024),
-        "journal_version": 3,
+        "journal_version": 4,
     }
     # Hardcoded design thresholds and algorithms are covered as well as taxonomy data.
     for name in ("draft", "source", "extract", "eligibility", "journal"):
@@ -232,15 +232,19 @@ def enumerate_advisories(github, journal):
     records = {}
     for ecosystem in source.ECOSYSTEMS:
         page = 1
+        next_url = None
         while True:
             key = f"{ecosystem}:{page}"
             if key not in journal.rows["advisories"]:
                 journal.boundary()
-                result = github.advisory_page(page, ecosystem=ecosystem)
-                journal.put("advisories", key, {"rows": [source.reduce_advisory(row) for row in result["rows"]], "done": result["done"]})
+                result = github.advisory_page(next_url, ecosystem=ecosystem)
+                journal.put(
+                    "advisories", key, {"rows": [source.reduce_advisory(row) for row in result["rows"]], "next_url": result["next_url"]}
+                )
             result = journal.rows["advisories"][key]
             records.update((row["ghsa_id"], row) for row in result["rows"])
-            if result["done"]:
+            next_url = result["next_url"]
+            if next_url is None:
                 break
             page += 1
     if not records: