## What Changed

- compute range-format support from formatter configuration and
language-server capabilities
- show `Format Selections` only when at least one selected buffer has a
range-capable formatter
- keep Prettier-supported range formatting available without depending
on LSP support
- hide the action for formatter modes that cannot honor selections, such
as external-command and code-action formatters
- keep the action handler safe by rechecking support and returning early
when range formatting is unavailable
- restrict capability checks to the servers actually registered for the
current buffer
- add regression coverage for supported, unsupported, and mixed-server
cases
- document when `Format Selections` is available in both action docs and
user docs


Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #25796

Release Notes:
- Improved `Format Selections` so it is only shown when the active
formatter supports range formatting.

Testing I did:

Here are the formatters I used:
<img width="829" height="434" alt="Screenshot_20260405_102047"
src="https://github.com/user-attachments/assets/cae4a238-277e-4188-873f-189e9f098699"
/>

Note: I've chosen three formatters:
1. Prettier, which supports range formatting
2. clangd (LSP) which also supports range formatting
3. gopls which do not support range formatting


[Screencast_20260405_102431.webm](https://github.com/user-attachments/assets/69ce3f95-0b73-46a0-853d-3b5be6329dde)

---------

Signed-off-by: Pratik Karki <pratik@prertik.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>