Skills cassette

Reference pages for Skills cassette, synced at build time from papercomputeco/skills-cassette. Each page is owned by that repo, so a behavior change and its documentation land in the same pull request there.

• Skills cassette — Stable skills, immutable private/public revisions, exact evaluation, and durable asynchronous generation.
• API reference — Stable skills, immutable revisions, visibility, latest resolution, and asynchronous generation.
• Deploying — Image identity, tenant-local dependencies, worker configuration, and durable storage.
• Development — Build and test from a checkout, and what the test suite pins about the manifest.