chore: prepare npm release package

[wesleysimplicio]

Summary

• exclude Python bytecode/cache artifacts from the npm package whitelist
• update the README release heading from 1.5 to 1.12
• update the documented Python test count to match the current suite

Refs #34

Validation

• npm test
• npm pack --dry-run --json with a bytecode/cache guard: 52 entries, no __pycache__ or .pyc files

Notes

• This does not publish to npm and intentionally does not close [Release] Publish 1.12.0 to npm (registry stuck at 1.1.0) #34. The registry publish still requires an authenticated npm token or the release workflow secret.