chore: verify CJS/ESM/TypeScript resolution in a clean consumer project

[mdesoto]

Split from #18.

Before or shortly after the first publish, verify that the package resolves correctly from a consumer's perspective using the packed tarball.

Tasks

• npm pack and install the tarball into a fresh project (npm install ./quarg-burnerguard-x.x.x.tgz)
• Verify require('@quarg/burnerguard') works (CJS)
• Verify import '@quarg/burnerguard' works (ESM)
• Verify TypeScript types resolve with moduleResolution: "node16" and "bundler"
• Verify dist/index.d.ts exports BurnerGuard and all public types
• Confirm no internal types or services leak through the public API

Context

npm pack --dry-run confirms the tarball contents are correct. This issue tracks the next step: end-to-end resolution testing from a real consumer project.