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/assistant2/src/assistant_settings.rs

@@ -4,6 +4,7 @@ use ::open_ai::Model as OpenAiModel;
 use anthropic::Model as AnthropicModel;
 use gpui::Pixels;
 use language_model::{CloudModel, LanguageModel};
+use lmstudio::Model as LmStudioModel;
 use ollama::Model as OllamaModel;
 use schemars::{schema::Schema, JsonSchema};
 use serde::{Deserialize, Serialize};
@@ -39,6 +40,11 @@ pub enum AssistantProviderContentV1 {
         default_model: Option<OllamaModel>,
         api_url: Option<String>,
     },
+    #[serde(rename = "lmstudio")]
+    LmStudio {
+        default_model: Option<LmStudioModel>,
+        api_url: Option<String>,
+    },
 }
 
 #[derive(Debug, Default)]
@@ -130,6 +136,12 @@ impl AssistantSettingsContent {
                                     model: model.id().to_string(),
                                 })
                             }
+                            AssistantProviderContentV1::LmStudio { default_model, .. } => {
+                                default_model.map(|model| LanguageModelSelection {
+                                    provider: "lmstudio".to_string(),
+                                    model: model.id().to_string(),
+                                })
+                            }
                         }),
                     inline_alternatives: None,
                     enable_experimental_live_diffs: None,
@@ -207,6 +219,18 @@ impl AssistantSettingsContent {
                             api_url,
                         });
                     }
+                    "lmstudio" => {
+                        let api_url = match &settings.provider {
+                            Some(AssistantProviderContentV1::LmStudio { api_url, .. }) => {
+                                api_url.clone()
+                            }
+                            _ => None,
+                        };
+                        settings.provider = Some(AssistantProviderContentV1::LmStudio {
+                            default_model: Some(lmstudio::Model::new(&model, None, None)),
+                            api_url,
+                        });
+                    }
                     "openai" => {
                         let (api_url, available_models) = match &settings.provider {
                             Some(AssistantProviderContentV1::OpenAi {
@@ -305,6 +329,7 @@ fn providers_schema(_: &mut schemars::gen::SchemaGenerator) -> schemars::schema:
         enum_values: Some(vec![
             "anthropic".into(),
             "google".into(),
+            "lmstudio".into(),
             "ollama".into(),
             "openai".into(),
             "zed.dev".into(),