fix: unnamed primary keys dropped and re-added on every incremental run

[sd-db]

What

An unnamed primary key (type: primary_key with no name) is auto-named by Databricks. On incremental runs the model carries name=None while the catalog read carries the server-assigned name, so ConstraintsConfig.get_diff never matched them and issued DROP CONSTRAINT ... CASCADE + re-add every run — silently dropping dependent foreign keys (and erroring with TABLE_OR_VIEW_NOT_FOUND under concurrent DDL, per the report).

This is the same class of bug as #1552 (RELY expression), on a different non-round-trippable field: the name.

Fix

• A primary key is now matched on its columns alone (a table has exactly one PK), so an unnamed PK adopts the catalog's server-assigned name instead of churning.
• A deliberate rename of a named PK (same columns, different name) is still reconciled — handled in get_diff, not the comparison key.
• dbt now warns when a foreign key is declared without a name, since unnamed FKs churn by the same mechanism. Not fixed here: FK columns aren't a unique key, so they can't be safely de-named — assigning a name avoids it.

Tests

• Unit: unnamed-PK no-op, named-PK rename reconciled, unnamed-FK warns, named-FK no-warn.
• Functional: the existing RELY cascade test now uses an unnamed RELY PK, so one test guards both [BUG]: Mismatch in PK & FK expression (e.g. RELY) triggers unnecessary constraint drops that crashes on incremental runs #1513 and TABLE_OR_VIEW_NOT_FOUND on constraint DROP during V2 incremental materialization #1333 (verified: reverting only the name-fix makes it fail).

Closes #1333.

[sd-db]

/integration-test

[github-actions]

Integration tests dispatched for PR #1554 by @sd-db. Track progress in the Actions tab.

[github-actions]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
dbt/adapters/databricks/relation_configs
constraints.py					78
Project Total

This report was generated by python-coverage-comment-action

[github-actions]

Integration results for PR #1554 — UC cluster ✅ success · SQL warehouse ✅ success · All-purpose cluster ✅ success · Shard coverage ✅ success

Run details.

[sd-db]

Closed in favour of #1561