[Other]: bundled orchestration skill guide tells agents to enable a Settings > Experimental toggle that no longer exists

### Details

The bundled `orchestration` skill guide still instructs agents to turn on a setting that no longer exists.

`skill-guides/orchestration.md:51` (`e5cd5bf5`):

> - The orchestration experimental feature must be enabled in Settings > Experimental.

At that same commit there is no such toggle: `grep -n "experimentalOrchestration\|orchestrationEnabled" src/shared/types.ts` returns nothing, and there is no orchestration entry in `src/renderer/src/components/settings/`.

This matters more than a normal stale doc because the audience is an agent, not a person. `orca skills get orchestration --full` serves this text as the authoritative guide, so an agent following it looks for a toggle it cannot find and can reasonably conclude the whole surface is unavailable — a person would just shrug and carry on.

**Repro**

```
orca skills get orchestration --full | grep -n "Experimental"
# -> the line above

# then look for the toggle in Settings > Experimental — it is not there
```

**Expected:** drop the line, or replace it with whatever the current gating is (if any).

Single-line docs fix. Happy to send it.