test(api): freeze the public package surface before 1.0 #35

Context

The package, production-removal, performance, Vite, React, Chromium, Firefox, Node, and Windows gates are green. Before the stable release, the five documented npm entrypoints need an explicit reviewable snapshot so generated declaration drift cannot silently change the public API.

Scope

• Snapshot all five exported entrypoints and the declaration files reachable from them.
• Snapshot package-level compatibility metadata that changes consumer behavior.
• Add a TypeScript verifier to the release gate.
• Document what is public, what remains internal, and what the beta snapshot does and does not guarantee.
• Keep the snapshot human-reviewable and deterministic.

Acceptance

• An intentional declaration or exports-map change produces a focused snapshot diff.
• An unacknowledged public API drift fails pnpm check.
• The packed package and public API verifier both pass.
• No JavaScript source files or new runtime dependencies are introduced.