Add LM Studio support to the Assistant (#23097)

#### Release Notes:

- Added support for [LM Studio](https://lmstudio.ai/) to the Assistant.

#### Quick demo:


https://github.com/user-attachments/assets/af58fc13-1abc-4898-9747-3511016da86a

#### Future enhancements:
- wire up tool calling (new in [LM Studio
0.3.6](https://lmstudio.ai/blog/lmstudio-v0.3.6))

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/assistant/Cargo.toml

@@ -52,6 +52,7 @@ language.workspace = true
 language_model.workspace = true
 language_model_selector.workspace = true
 language_models.workspace = true
+lmstudio = { workspace = true, features = ["schemars"] }
 log.workspace = true
 lsp.workspace = true
 markdown.workspace = true