feat(vitest): add automatic suite enforcement

[wscourge]

Summary

• add a side-effectful qguard/vitest/setup entry point that installs qguard and wraps every Vitest test in an isolated query-tracking context
• export qguardSetup from qguard/vitest for a clean setupFiles: [qguardSetup] configuration
• fail only the offending test with the existing QueryGuardError, including configured notification dispatch and test metadata
• cover clean tests, automatic failures, concurrent-test isolation, and user beforeEach/afterEach hooks with real nested Vitest runs
• document automatic setup, opt-out, lifecycle boundaries, and the explicit assertion APIs

Usage

// vitest.config.ts
import { defineConfig } from 'vitest/config'
import { qguardSetup } from 'qguard/vitest'

export default defineConfig({
  test: {
    setupFiles: [qguardSetup],
  },
})

Vitest resolves setupFiles strings relative to the project root rather than through package exports. qguardSetup therefore exposes the absolute path to the new qguard/vitest/setup entry point.

The setup module deliberately installs drivers with top-level await and keeps its beforeEach hook synchronous. Entering AsyncLocalStorage after an awaited hook does not propagate the context back into Vitest's test runner.

Verification

• typecheck passed
• Biome passed for src/ and all new tests/fixtures
• unit suite: 246 tests passed
• PostgreSQL + MySQL integration suite: 15 tests passed
• production build passed
• packed artifact contains the setup entry point and remains under the 40 KB gate (34,118 bytes)
• packed consumer verified against Vitest 1.0.4; repository coverage runs on Vitest 3.2.4

Closes #9