## Why
Fast mode previously gated both Fast and Ultra Fast, preventing policies from allowing one while disabling the other.
## What changed
- Add the default-enabled `features.ultrafast_mode` flag and enforce it independently of `features.fast_mode` in service-tier selection, requests, and agent prewarming.
- Filter TUI service-tier commands and selections by the corresponding policy and model catalog support.
- Report `supportsIndependentSpeedModes: true` from `configRequirements/read` and update the protocol schemas and generated bindings. Retain the shared Fast gate when connecting to older servers that omit this capability.
- Preserve legacy cloud speed denials by translating `rbac-fast-mode` fragments with `fast_mode = false` into a denial of both modes, while retaining higher-priority enterprise overrides.
## Testing
Add coverage for all four Fast/Ultra Fast policy combinations in requirements responses and request routing, agent prewarm inheritance, TUI command visibility and saved selections, and legacy cloud denial normalization and override precedence.
GitOrigin-RevId: 147e08524c4b228ea9d46b25a9f8aa64c359e169
