feat: add ultracode session config option (#1438)

Adds an **Ultracode** session config option. It turns on Claude Code's
dynamic workflows for every task, at any effort level. Clients that
support boolean config options get a native switch; the rest get an
On/Off select. This follows the Fast mode pattern.

## How the CLI handles ultracode (2.1.310, checked against the bundled
binary and a live session)

- **Which models:** ultracode works on exactly the models that support
`xhigh` effort. The CLI uses the same check for both. So Opus 4.7+,
Sonnet 5+, Haiku 5.5 and Fable qualify; Opus 4.6 and Haiku 4.5 don't.
Effort level no longer matters.
- **Workflows:** dynamic workflows must be enabled. They are off by
default on Pro plans, and org or managed policy can turn them off.
- **State reporting:** `query.getSettings()` returns
`applied.ultracodeAvailable` and `applied.ultracodeRequested`. The CLI's
schema says hosts should "offer an Ultracode control only while this is
true". This method exists at runtime but is missing from the SDK's
`.d.ts`, so the adapter reads it with a cast and falls back to settings
and model data when it is absent.
- **Unsupported requests:** `applyFlagSettings({ultracode})` is never
validated. The request is stored and stays in place across model
switches; it takes effect whenever the model supports it.
- **Effort changes:** an `effortLevel` change sent without an
`ultracode` key turns ultracode off.

## Behavior

- **Visibility:** at session start, one `getSettings()` call decides
availability and the starting value. Model switches combine the
workflows result learned at start with the new model's
`supportedEffortLevels`, so the switch path makes no extra control
request.
- **Value:** the session tracks the user's choice, like
`fastModeEnabled`. The option hides on unsupported models and comes back
with the same value.
- **Effort applies:** `effortFlagSettings` now carries the session's
toggle instead of `settings.ultracode`. This applies at the initial
apply, on model switch, and from the effort picker, so effort changes no
longer turn ultracode off.
- **Clear context:** the clear-context restart restores the toggle, as
it does Fast mode.

## Known limitation

If a user types `/effort ultracode on` as a prompt, the toggle does not
update. The adapter already doesn't pick up effort changes typed as
`/effort` commands.

## Testing

- New `src/tests/ultracode-config.test.ts`. It covers the helpers and
session behavior: seeding from the CLI's report, hiding while workflows
are off, following the model's support, keeping the value across effort
and model switches, and rejected applies.
- New clear-context restore test. `effortFlagSettings` tests updated.
- Live probe against CLI 2.1.310 confirmed the `getSettings` fields, the
`xhigh` proxy (`claude-opus-4-6` reports unavailable while the request
stays in place), and the effort/key behavior.
- `npm run check`, `npm run build`, `npm run test:run` all pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/air-extensions.md

@@ -707,7 +707,7 @@ A non-empty plan also gets one clear-context choice with the same priority.
 After that choice, the adapter stops the old private Claude query and hides that internal rejection.
 It starts a new private query under the same ACP session.
 It continues the turn with `Implement the following plan:` and the complete plan.
-The mode, model, agent, effort, Fast mode, and turn usage stay the same.
+The mode, model, agent, effort, Fast mode, ultracode, and turn usage stay the same.
 The SDK cannot apply `allowedPrompts` again, so those hints do not survive the handoff.
 
 The adapter does not allow a callback only because the session mode is `bypassPermissions`.