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/src/inline_assistant.rs

@@ -34,8 +34,8 @@ use gpui::{
 };
 use language::{Buffer, IndentKind, Point, Selection, TransactionId, line_diff};
 use language_model::{
-    LanguageModel, LanguageModelRegistry, LanguageModelRequest, LanguageModelRequestMessage,
-    LanguageModelTextStream, Role, report_assistant_event,
+    ConfiguredModel, LanguageModel, LanguageModelRegistry, LanguageModelRequest,
+    LanguageModelRequestMessage, LanguageModelTextStream, Role, report_assistant_event,
 };
 use language_model_selector::{LanguageModelSelector, LanguageModelSelectorPopoverMenu};
 use multi_buffer::MultiBufferRow;
@@ -312,7 +312,9 @@ impl InlineAssistant {
                 start..end,
             ));
 
-            if let Some(model) = LanguageModelRegistry::read_global(cx).active_model() {
+            if let Some(ConfiguredModel { model, .. }) =
+                LanguageModelRegistry::read_global(cx).default_model()
+            {
                 self.telemetry.report_assistant_event(AssistantEvent {
                     conversation_id: None,
                     kind: AssistantKind::Inline,
@@ -877,7 +879,9 @@ impl InlineAssistant {
             let active_alternative = assist.codegen.read(cx).active_alternative().clone();
             let message_id = active_alternative.read(cx).message_id.clone();
 
-            if let Some(model) = LanguageModelRegistry::read_global(cx).active_model() {
+            if let Some(ConfiguredModel { model, .. }) =
+                LanguageModelRegistry::read_global(cx).default_model()
+            {
                 let language_name = assist.editor.upgrade().and_then(|editor| {
                     let multibuffer = editor.read(cx).buffer().read(cx);
                     let multibuffer_snapshot = multibuffer.snapshot(cx);
@@ -1629,8 +1633,8 @@ impl Render for PromptEditor {
                                 format!(
                                     "Using {}",
                                     LanguageModelRegistry::read_global(cx)
-                                        .active_model()
-                                        .map(|model| model.name().0)
+                                        .default_model()
+                                        .map(|default| default.model.name().0)
                                         .unwrap_or_else(|| "No model selected".into()),
                                 ),
                                 None,
@@ -2077,7 +2081,7 @@ impl PromptEditor {
         let disabled = matches!(codegen.status(cx), CodegenStatus::Idle);
 
         let model_registry = LanguageModelRegistry::read_global(cx);
-        let default_model = model_registry.active_model();
+        let default_model = model_registry.default_model().map(|default| default.model);
         let alternative_models = model_registry.inline_alternative_models();
 
         let get_model_name = |index: usize| -> String {
@@ -2183,7 +2187,9 @@ impl PromptEditor {
     }
 
     fn render_token_count(&self, cx: &mut Context<Self>) -> Option<impl IntoElement> {
-        let model = LanguageModelRegistry::read_global(cx).active_model()?;
+        let model = LanguageModelRegistry::read_global(cx)
+            .default_model()?
+            .model;
         let token_counts = self.token_counts?;
         let max_token_count = model.max_token_count();
 
@@ -2638,8 +2644,9 @@ impl Codegen {
         }
 
         let primary_model = LanguageModelRegistry::read_global(cx)
-            .active_model()
-            .context("no active model")?;
+            .default_model()
+            .context("no active model")?
+            .model;
 
         for (model, alternative) in iter::once(primary_model)
             .chain(alternative_models)
@@ -2863,7 +2870,9 @@ impl CodegenAlternative {
         assistant_panel_context: Option<LanguageModelRequest>,
         cx: &App,
     ) -> BoxFuture<'static, Result<TokenCounts>> {
-        if let Some(model) = LanguageModelRegistry::read_global(cx).active_model() {
+        if let Some(ConfiguredModel { model, .. }) =
+            LanguageModelRegistry::read_global(cx).inline_assistant_model()
+        {
             let request = self.build_request(user_prompt, assistant_panel_context.clone(), cx);
             match request {
                 Ok(request) => {