eval: Fine-grained assertions (#29246)

- Support programmatic examples
([example](17feb260a0/crates/eval/src/examples/file_search.rs))
- Combine data-driven example declarations into a single `.toml` file
([example](17feb260a0/crates/eval/src/examples/find_and_replace_diff_card.toml))
- Run judge on individual assertions (previously called "criteria")
- Report judge and programmatic assertions in one combined table

Note: We still need to work on concept naming 

<img width=400
src="https://github.com/user-attachments/assets/fc719c93-467f-412b-8d47-68821bd8a5f5">

Release Notes:

- N/A

---------

Co-authored-by: Richard Feldman <oss@rtfeldman.com>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Thomas Mickley-Doyle <tmickleydoyle@gmail.com>

crates/agent/src/thread.rs

@@ -315,6 +315,7 @@ pub struct Thread {
     request_callback: Option<
         Box<dyn FnMut(&LanguageModelRequest, &[Result<LanguageModelCompletionEvent, String>])>,
     >,
+    remaining_turns: u32,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -368,6 +369,7 @@ impl Thread {
             message_feedback: HashMap::default(),
             last_auto_capture_at: None,
             request_callback: None,
+            remaining_turns: u32::MAX,
         }
     }
 
@@ -442,6 +444,7 @@ impl Thread {
             message_feedback: HashMap::default(),
             last_auto_capture_at: None,
             request_callback: None,
+            remaining_turns: u32::MAX,
         }
     }
 
@@ -522,7 +525,7 @@ impl Thread {
         self.messages.iter().find(|message| message.id == id)
     }
 
-    pub fn messages(&self) -> impl Iterator<Item = &Message> {
+    pub fn messages(&self) -> impl ExactSizeIterator<Item = &Message> {
         self.messages.iter()
     }
 
@@ -958,7 +961,21 @@ impl Thread {
         })
     }
 
+    pub fn remaining_turns(&self) -> u32 {
+        self.remaining_turns
+    }
+
+    pub fn set_remaining_turns(&mut self, remaining_turns: u32) {
+        self.remaining_turns = remaining_turns;
+    }
+
     pub fn send_to_model(&mut self, model: Arc<dyn LanguageModel>, cx: &mut Context<Self>) {
+        if self.remaining_turns == 0 {
+            return;
+        }
+
+        self.remaining_turns -= 1;
+
         let mut request = self.to_completion_request(cx);
         if model.supports_tools() {
             request.tools = {