Closes#59620
## Problem
A language whose name contains a `/`, such as a custom `PL/X` extension
(`lsp_id` → `pl/x`), broke snippets end to end:
- The `snippets: configure snippets` action wrote the file to
`~/.config/zed/snippets/pl/x.json`, i.e. inside a `pl/` subdirectory.
- The snippet scanner reads `snippets/` non-recursively and skips
directories, so that file was never loaded and the snippet could never
be used.
- The completion lookup keyed off the raw `lsp_id` (`pl/x`), which
wouldn't have matched the file-stem key even if the file had been
scanned.
So Zed's own UI created a snippet file it could never read back.
## Fix
Add `LanguageName::snippet_scope_id()` (the `lsp_id` with `/` and `\`
removed) and use it everywhere a language maps to its snippet file name
or lookup key:
- the Configure Snippets writer and its "already configured" label, and
- the two completion lookups in `editor`.
`PL/X` now maps to a flat `plx.json`, as suggested in the issue. The
`editor::InsertSnippet` action is intentionally left unchanged: its
`language` field is documented to be the snippet file name stem, which
is already separator-free.
Note: files created under the old behavior (nested `foo/bar.json`)
aren't migrated; re-running Configure Snippets writes the corrected flat
file.
## Testing
- Added a `language_core` unit test asserting `snippet_scope_id()`
strips `/` and `\` (e.g. `PL/X` → `plx`).
- `cargo test -p language_core` passes.
- `./script/clippy -p language_core -p language` passes.
- Docs Prettier passes.
Release Notes:
- Fixed snippets being unusable for languages whose name contains a `/`
character
Ibrahim Khan
cbe92a9c1a