This PR adds an initial version of using `@` in the message editor to
add context to the thread.
We don't yet insert any sort of reference to it in the message body
itself.
Release Notes:
- N/A
This PR sketches in the structure for the directory context picker.
Waiting on implementing the actual behavior until we fix the issues with
the file context picker.
Release Notes:
- N/A
This PR wire up the context picker with the inline assist.
UI is not finalized.
Release Notes:
- N/A
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Co-authored-by: Richard <richard@zed.dev>
Co-authored-by: Agus <agus@zed.dev>

- Adds the Switch component
- Updates `Selected`, `Selectable` -> `ToggleState`, `Toggleable`
- Adds `checkbox` and `switch` functions to align better with other
elements in our layout system.
We decided not to merge Switch and Checkbox. However, in a followup I'll
introduce a Toggle or AnyToggle enum so we can update
`CheckboxWithLabel` -> `ToggleWithLabel` as this component will work
exactly the same with either a Checkbox or a Switch.
Release Notes:
- N/A