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/agent/src/terminal_codegen.rs

@@ -2,7 +2,9 @@ use crate::inline_prompt_editor::CodegenStatus;
 use client::telemetry::Telemetry;
 use futures::{SinkExt, StreamExt, channel::mpsc};
 use gpui::{App, AppContext as _, Context, Entity, EventEmitter, Task};
-use language_model::{LanguageModelRegistry, LanguageModelRequest, report_assistant_event};
+use language_model::{
+    ConfiguredModel, LanguageModelRegistry, LanguageModelRequest, report_assistant_event,
+};
 use std::{sync::Arc, time::Instant};
 use telemetry_events::{AssistantEvent, AssistantKind, AssistantPhase};
 use terminal::Terminal;
@@ -31,7 +33,9 @@ impl TerminalCodegen {
     }
 
     pub fn start(&mut self, prompt: LanguageModelRequest, cx: &mut Context<Self>) {
-        let Some(model) = LanguageModelRegistry::read_global(cx).active_model() else {
+        let Some(ConfiguredModel { model, .. }) =
+            LanguageModelRegistry::read_global(cx).inline_assistant_model()
+        else {
             return;
         };