Generate and verify v8-to-v9 migration documentation

Build and prove the documentation in three stages:

1. Inventory every public v8 component and determine its v9 destination.
2. Inspect authoritative v8 and v9 source, then create or correct the per-component migration guide.
3. Give a migration agent only one v8 microcase and its relevant guide, then evaluate the generated v9 code against a hidden source-derived checklist.

Keep manifests, generated migrations, evaluation ledgers, and runner artifacts outside the Fluent UI checkout. Only documentation and skill corrections belong in the documentation pull request.

Completion standard

Do not describe the documentation as exhaustive until: