docs: enforce API documentation coverage

[SomSamantray]

Summary

API documentation coverage is now enforced as a deterministic, package-aware build gate.

• Adds TypeDoc coverage analysis with a committed baseline ratchet that fails closed on missing packages, undocumented symbols, malformed input, and public API surface changes.
• Documents shared types, storage, autoscaling, and browser-controller APIs while repairing affected logging links.
• Adds focused regression coverage for inherited documentation, generated-data failures, and reflection replacements.

Validation

• yarn vitest run test/api-documentation-coverage.test.mts — 9 passed
• yarn tsc-check-tests
• yarn lint
• yarn format:check
• Website build — 1989/2812 reflections covered (70.7%)

New concepts

A baseline ratchet treats generated API reflection keys as a compatibility surface: coverage can improve, but public symbols cannot silently disappear or be replaced. This is useful when generated documentation is the source of truth; it is unnecessary for purely hand-authored docs.

Related: #3884