db: rename the four double-prefixed CHECK constraints (#3275)

Run 5026 got the models-vs-chain diff to 7 lines. Three findings, and one
of them reverses an assumption I made in the previous commit.

The doubled CHECK names are what the DATABASE has, not what the generator
invented. base.py's convention is ck_%(table_name)s_%(constraint_name)s,
which — unlike uq/fk/ix — applies even to a constraint that already has a
name, so four migrations that passed an already-prefixed name got it
prefixed twice:

    ck_import_settings_ck_import_settings_singleton
    ck_ml_settings_ck_ml_settings_singleton
    ck_post_ck_post_translation_override
    ck_tag_ck_tag_fandom_requires_character

The workflow repair added last commit is still correct and still needed —
autogenerate really does re-double a name on the round trip — but it was
making the MODELS side clean against a chain that is dirty. The
comment in ml_settings.py claiming its bare name "matches migration 0003"
was simply false; 0003 produces the doubled form.

Nothing reads a CHECK constraint by name, so this has never done harm.
But it is precisely the development-era residue the collapsed baseline
exists to leave behind, and a public schema should not ship it — so 0088
renames the deployed constraints and all six models now declare bare
names. RENAME CONSTRAINT is catalog-only: no scan, no rewrite, no
revalidation, which is why this is safe on post and tag. Guarded on
pg_constraint scoped by conrelid, so it is a no-op on a database built
from the models.

ix_tag_fandom_id showed as a difference only because chain_ref was pinned
to 0a5bbe8, which predates 0088 — the comparison was measuring the models
against a chain missing the migration that closes the gap. chain_ref now
defaults to blank, meaning "the chain in this ref". Pin it to a commit
only after the collapse, when the tree no longer carries the revisions.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017QHszn9H8VBvx5Ke8x1hvw

.forgejo/workflows/baseline.yml

@@ -34,9 +34,9 @@ on:
   workflow_dispatch:
     inputs:
       chain_ref:
-        description: 'Commit/tag that still carries the full 0001..0087 chain'
+        description: 'Commit/tag carrying the full chain; blank = this ref (use a pinned commit only AFTER the collapse)'
         type: string
-        default: '0a5bbe8'
+        default: ''
       mode:
         description: 'chain = compare against this tree''s migrations; models = compare against a schema built from the MODELS'
         type: string
@@ -100,10 +100,15 @@ jobs:
       - name: Build the schema the OLD chain produces
         env:
           CHAIN_REF: ${{ github.event.inputs.chain_ref }}
+          THIS_SHA: ${{ github.sha }}
         run: |
           set -eux
           docker exec "$PG_CONTAINER" createdb -U fabledcurator fc_chain
-          git worktree add /tmp/chain "$CHAIN_REF"
+          # Blank means "the chain in this ref", which is what you want while
+          # the chain is still intact — comparing the models against a PINNED
+          # older commit reports every migration written since as a difference.
+          # Pin it only after the collapse, when the tree no longer has them.
+          git worktree add /tmp/chain "${CHAIN_REF:-$THIS_SHA}"
           ls /tmp/chain/alembic/versions/*.py | wc -l
           cd /tmp/chain
           DB_NAME=fc_chain alembic upgrade head