Harden production quality gates and persistence reliability

[deepfates]

Summary

• add production CI workflow (build, lint, test, coverage)
• add release hygiene files (LICENSE, CHANGELOG.md) and package metadata improvements
• split lint scope to publishable library code via tsconfig.lint.json and add optional lint:bench
• expand tests from 7 to 12 with persistence and edge-case coverage
• harden HNSWWithDB lifecycle: explicit close(), delete/reinit sequencing, and explicit uninitialized DB errors
• improve README with API reference, tuning guidance, limitations, and corrected IndexedDB example

Validation

• npm run build
• npm run lint
• npm test -- --runInBand
• npm run test:coverage

Coverage

• statements: 93.66%
• branches: 74.78%
• functions: 98.3%
• lines: 94.6%