fix(combos): clear LKGP pins on delete

[KrzysiekSko]

Summary

• Cleans up LKGP key_value rows when a persisted combo is deleted.
• Preserves unrelated LKGP state, including prefix-sharing combo names and names containing SQLite LIKE wildcards.
• Adds regression coverage for deleted, unrelated, nonexistent, cached, and no-pin delete paths.

Problem

deleteCombo() deleted the combo row but did not delete LKGP pins keyed by that combo name. The result was unreachable key_value rows under namespace = 'lkgp' after the combo no longer existed.

Root Cause

LKGP pins are stored as key = "${comboName}:${modelId}". Existing cleanup helpers either delete one exact comboName:modelId pair (clearLKGP()), all LKGP (clearAllLKGP()), or pins by provider connection id (deleteLKGPByConnectionIds()). deleteCombo() only executed DELETE FROM combos WHERE id = ?, so it never removed rows that belonged exclusively to the deleted combo name.

Solution

• Add a combo-name LKGP cleanup helper that deletes keys under the exact ${comboName}: namespace prefix.
• Escape %, _, and \\ in the SQLite LIKE pattern and rely on the : delimiter to avoid collateral deletion.
• Run combo-row deletion and LKGP-row deletion in one SQLite transaction, then invalidate LKGP read-cache entries for the deleted keys.

Invariant

DELETE COMBO X → REMOVE LKGP STATE OWNED BY X

AND

UNRELATED LKGP STATE → PRESERVED

Forbidden state:

DELETED COMBO → ORPHANED LKGP REFERENCE

Regression Evidence

• Before the fix, tests/unit/combo-delete-lkgp-cleanup-12326.test.ts failed: deleted combo LKGP rows still returned { provider: 'berry', connectionId: 'conn-1' } instead of null.
• After the fix, the focused regression test passes.
• Sabotage check performed by temporarily reverting the deleteCombo() cleanup while keeping the test: focused test failed again; after restoring the fix it passed again.

Behavior Proof

• deleted combo pins removed
• unrelated combo pins preserved
• prefix-sharing names preserved
• cache invalidated correctly for deleted keys
• nonexistent/no-pin behavior remains safe

Validation

• node --import tsx/esm --test tests/unit/combo-delete-lkgp-cleanup-12326.test.ts
• node --import tsx/esm --test tests/unit/combo-delete-lkgp-cleanup-12326.test.ts tests/unit/combo-cache-invalidation.test.ts
• npm run typecheck:core
• npx eslint src/lib/db/repositories/sqliteComboRepository.ts src/lib/db/settings/lkgp.ts src/lib/db/settings.ts tests/unit/combo-delete-lkgp-cleanup-12326.test.ts
• git diff --check

Scope / Risk

Low scope: persistence cleanup only. No routing-provider, circuit-breaker, API-key ACL, authz, or provider-plugin behavior changed.

Compatibility

No schema migration and no public LKGP contract change. Existing LKGP key format is preserved.

Fixes #12326