ai: Separate model settings for each feature (#28088)

Closes: https://github.com/zed-industries/zed/issues/20582

Allows users to select a specific model for each AI-powered feature:
- Agent panel
- Inline assistant
- Thread summarization
- Commit message generation

If unspecified for a given feature, it will use the `default_model`
setting.

Release Notes:

- Added support for configuring a specific model for each AI-powered
feature

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

crates/assistant_tools/src/edit_files_tool.rs

@@ -9,7 +9,7 @@ use collections::HashSet;
 use edit_action::{EditAction, EditActionParser, edit_model_prompt};
 use futures::{SinkExt, StreamExt, channel::mpsc};
 use gpui::{App, AppContext, AsyncApp, Entity, Task};
-use language_model::LanguageModelToolSchemaFormat;
+use language_model::{ConfiguredModel, LanguageModelToolSchemaFormat};
 use language_model::{
     LanguageModelRegistry, LanguageModelRequest, LanguageModelRequestMessage, MessageContent, Role,
 };
@@ -205,8 +205,8 @@ impl EditToolRequest {
         cx: &mut App,
     ) -> Task<Result<String>> {
         let model_registry = LanguageModelRegistry::read_global(cx);
-        let Some(model) = model_registry.editor_model() else {
-            return Task::ready(Err(anyhow!("No editor model configured")));
+        let Some(ConfiguredModel { model, .. }) = model_registry.default_model() else {
+            return Task::ready(Err(anyhow!("No model configured")));
         };
 
         let mut messages = messages.to_vec();