User-facing command tying the contract together: `options`/`status` show
providers with GBrain first and live availability, `select <provider>`
persists the choice, `consent [path]` records per-repo indexing consent,
`index [path]` registers + indexes the repo with the selected provider
(refusing non-local providers until consented), and `search <query>` runs a
query, degrading with a clear message when the provider is unavailable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
