fix(review): address PR #16 code-review findings

#1 ingest: normalize the pinned caller id (_norm_cited_id) so a non-bare DOI caller cannot store a URL-form papers.id that defeats DQ-5 idempotency / the startswith(10.) recovery gates. #2 quality.section_label: collapse to a controlled bucket only for an EXACT canonical heading; descriptive titles ('Abstract Nonsense...') keep their real title instead of being mislabelled. #4 ra_grobid_backfill: release the read connection before the slow GROBID network loop, fresh connection for the write (no idle-in-transaction across the loop over the flaky tunnel).

#5/#10 tex: flatten_inputs strips unresolved input/include at the depth cap (no literal leak on cycles); _norm_texkey strips only a single leading ./ . #6/#7 arxiv.fetch_source: keep non-.tex members resolvable for input; pick primary on an UN-commented documentclass line. #13 is_arxiv_id: also exclude http:// and arXiv-DOI forms. Tests added/updated for each.

Left as deliberate decisions: #3 (pre-section text drop is pre-existing in extract_sections; abstract stored separately), #8 (script normalizer is intentionally self-contained, already documented), #9/#11/#12 (no current trigger / tightening the gzip heuristic would reject valid old LaTeX like documentstyle / title truncation is by design on a write-only column). ruff + mypy clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/ingest/test_ingest.py

@@ -238,11 +238,15 @@ def test_ingest_paper_source_tex(tmp_path: Any) -> None:
     chunk_sql: str = chunk_insert_call[0][0]
     assert "INSERT INTO chunks" in chunk_sql
 
-    # R-F: heading → controlled bucket where it maps ("Introduction"→intro,
-    # "Proof of…"→proof), else the cleaned real title ("discrete conformal maps")
-    # instead of collapsing to "body".
+    # R-F: a bare canonical heading → bucket ("Introduction"→intro); any other
+    # heading is stored as its cleaned real title ("proof of the main theorem",
+    # "discrete conformal maps") instead of being collapsed/mislabelled.
     chunk_rows = chunk_insert_call[0][1]
-    assert [row[4] for row in chunk_rows] == ["intro", "proof", "discrete conformal maps"]
+    assert [row[4] for row in chunk_rows] == [
+        "intro",
+        "proof of the main theorem",
+        "discrete conformal maps",
+    ]
     assert result.chunks_upserted == len(section_pairs)