[codex] test cache behavior for batched mutations

[Saiaaax]

Summary

• Add focused regression tests for SQL batches that combine a read with a mutation.
• Verify beforeQueryCache does not read cached data for a SELECT; DELETE batch.
• Verify afterQueryCache does not write results for the same batch, including the optional-params path.
• Include a 9-second validation demo.

Why

node-sql-parser returns an AST array for multi-statement SQL. hasModifyingStatement recursively detects mutations in that array, but the behavior had no regression coverage. If it regressed, a batch containing a write could incorrectly interact with the query cache.

Validation

• node node_modules/vitest/vitest.mjs --run src/cache/index.test.ts — 16 tests passed.
• node node_modules/prettier/bin/prettier.cjs --check src/cache/index.test.ts — passed.
• Full coverage run: 153 tests passed; the same four pre-existing RLS assertions fail on main. Cache branch coverage increased from 81.39% to 86.04%; global branch coverage increased from 47.68% to 47.99%.
• git diff --check — passed.

AI-assisted with Codex; the diff and test behavior were reviewed locally.

/claim #71

[Saiaaax]

/claim #71