fix(ingest): canonicalise papers.id to the caller id (audit C-7, T-3)

openalex.fetch_paper fills paper.id from OpenAlex's URL-form doi/id
(e.g. https://doi.org/10.48550/arxiv.math/0603097), and ingest upserted that as
papers.id. Live DB confirmed 35/36 ids were URL-form — breaking bare-id lookups
(graph related / discover citing / search by id) and leaving cited_id matching
to rely solely on openalex_id.

ingest now sets paper.id to the caller-supplied id (the arXiv id / DOI the CLI
and ingest scripts use); OpenAlex's work id is retained as openalex_id and in
paper_identifiers. Regression test: fetch_paper returns a URL-form id, papers.id
upsert uses the bare caller id.

T-3: the OpenAlex test fixture used a bare 'doi' (not the URL form the API
emits) and never asserted paper.id, which masked this. Fixture now uses the URL
form and the test pins fetch_paper's mapping.

NOTE: existing rows keep their URL-form ids until re-ingested — run ingest_all.sh
to migrate the 36-paper corpus (chosen migration path).

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

codex/ingest.py

@@ -98,6 +98,14 @@ def ingest_paper(
     if paper is None:
         raise ValueError(f"Paper not found: {paper_id}")
 
+    # Canonical identity is the caller-supplied id — what the CLI / ingest scripts
+    # use and what papers.id is contracted to hold (arXiv id or DOI). OpenAlex's
+    # fetch_paper fills paper.id with the URL-form doi/id (e.g.
+    # "https://doi.org/10.48550/arxiv.math/0603097"), which broke bare-id lookups
+    # and cross-citation matching (audit C-7). The OpenAlex work id is retained
+    # separately as openalex_id and in the paper_identifiers alias table.
+    paper.id = paper_id.strip()
+
     # Auto-generate bibkey when source has none (D-04).
     if paper.bibkey is None:
         paper.bibkey = _make_bibkey(paper)