Legislation axis: Bill schema, OpenStates ingest, validator + provenance

The legislative-process corpus, parallel to the U.S. Code statute corpus.
schemas/bill.schema.json + scripts/ingest_legislation.py (deterministic,
stdlib-only, reads per-state JSONL from the depot); validate.py gains
legislation/ as a third tree; Makefile 'legislation' target. Raw JSONL stays
off-repo on the depot (gitignored); the per-state SHA-256 manifest is the
committed provenance anchor. Vintage 2026-07-01.

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

.gitignore

@@ -7,3 +7,8 @@
 # "raw-first, in-repo" discipline turns on at v1.0 — see README.
 data/legal/raw/**/*.zip
 data/legal/raw/**/*.xml
+# Legislation (OpenStates): per-state enacted exports are the raw bytes
+# (~1.1GB/vintage), kept on the depot at /depot/exports/legislation/<vintage>/;
+# ingest reads them from there. Only the manifest (committed under data/sources/)
+# + the rendered Bill nodes get committed.
+data/legislation/