fix(brainztableinator): widen MusicBrainz Discogs ID columns to BIGINT

[SimplicityGuy]

Problem

Brainztableinator fails to insert MusicBrainz records with integer out of range — most visibly on releases. With requeue=True, the failing message loops forever.

Root cause: The extractor extracts Discogs IDs as i64 (extractor/src/jsonl_parser.rs:33), and Discogs IDs have crossed the int4 ceiling (2,147,483,647). But the musicbrainz schema declared the four Discogs-ID columns as INTEGER:

• musicbrainz.artists.discogs_artist_id
• musicbrainz.labels.discogs_label_id
• musicbrainz.releases.discogs_release_id
• musicbrainz.release_groups.discogs_master_id

These columns are written directly by brainztableinator.py (lines 523, 568, 602, 639).

Fix

Both halves are required:

1. CREATE TABLE columns → BIGINT — fixes fresh deployments.
2. _MUSICBRAINZ_MIGRATIONS (ALTER COLUMN … TYPE BIGINT) — fixes existing deployments. CREATE TABLE IF NOT EXISTS never alters a pre-existing table, so already-deployed databases keep their int4 columns without an explicit ALTER. ALTER … TYPE BIGINT performs no table rewrite when the column is already BIGINT, so it is safe to run on every startup. Ordered after table creation and before the indexes that reference these columns.

Tests

• New TestMusicBrainzDiscogsIdColumns: asserts CREATE TABLE uses BIGINT, a widening migration exists per column, one migration per column, and correct execution ordering (tables → migrations → indexes).
• Idempotency check updated to exempt ALTER … TYPE (inherently idempotent, no IF NOT EXISTS form exists).
• Statement-count assertions updated for the added migrations.
• brainztableinator/README.md schema docs updated to BIGINT.

All schema-init tests pass; uv run mypy . clean; pre-commit hooks pass.

🤖 Generated with Claude Code

https://claude.ai/code/session_01DipaE4GgAEomY77fw9tWDk

[SimplicityGuy]

Closing as superseded — this fix was already merged to main via #376 (identical BIGINT columns + ALTER COLUMN migrations + README update). No functional difference remains.