Allow Anthropic custom models to override temperature (#18160)

Release Notes:

- Allow Anthropic custom models to override "temperature"

This also centralized the defaulting of "temperature" to be inside of
each model's `into_x` call instead of being sprinkled around the code.

crates/assistant/src/context.rs

@@ -2180,7 +2180,7 @@ impl Context {
             messages: Vec::new(),
             tools: Vec::new(),
             stop: Vec::new(),
-            temperature: 1.0,
+            temperature: None,
         };
         for message in self.messages(cx) {
             if message.status != MessageStatus::Done {

crates/assistant/src/inline_assistant.rs

@@ -2732,7 +2732,7 @@ impl CodegenAlternative {
             messages,
             tools: Vec::new(),
             stop: Vec::new(),
-            temperature: 1.,
+            temperature: None,
         })
     }
 

crates/assistant/src/prompt_library.rs

@@ -796,7 +796,7 @@ impl PromptLibrary {
                                     }],
                                     tools: Vec::new(),
                                     stop: Vec::new(),
-                                    temperature: 1.,
+                                    temperature: None,
                                 },
                                 cx,
                             )

crates/assistant/src/slash_command/auto_command.rs

@@ -216,7 +216,7 @@ async fn commands_for_summaries(
         }],
         tools: Vec::new(),
         stop: Vec::new(),
-        temperature: 1.0,
+        temperature: None,
     };
 
     while let Some(current_summaries) = stack.pop() {

crates/assistant/src/terminal_inline_assistant.rs

@@ -284,7 +284,7 @@ impl TerminalInlineAssistant {
             messages,
             tools: Vec::new(),
             stop: Vec::new(),
-            temperature: 1.0,
+            temperature: None,
         })
     }