Add new action to run agent eval (#29158)

The old one wasn't linking, and
https://github.com/zed-industries/zed/pull/29081 has a bunch of merge
conflicts. Wanted to start simple/small.

## Todo

* [x] Remove low-signal examples
* [x] Make the eval run on a cron, on main, and on any PR with the
`run-eval` label
* [x] Noise in logs about failure to write settings
    ```
[2025-04-21T20:45:04Z ERROR settings] Failed to write settings to file
"/home/runner/.config/zed/settings.json"
    
       Caused by:
No such file or directory (os error 2) at path
"/home/runner/.config/zed/.tmpLewFEs"
    ```
* [x] `Agentic loop stalled`
(https://github.com/zed-industries/zed/actions/runs/14581044243/job/40897622894)
* [x] Make sure that events are recorded in snowflake
* [ ] Change judge criteria to be more explicit about meanings of scores

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Thomas Mickley-Doyle <tmickleydoyle@gmail.com>

crates/agent/src/active_thread.rs

@@ -1010,6 +1010,7 @@ impl ActiveThread {
                 }
             }
             ThreadEvent::CheckpointChanged => cx.notify(),
+            ThreadEvent::ReceivedTextChunk => {}
         }
     }
 

crates/agent/src/thread.rs

@@ -1231,6 +1231,7 @@ impl Thread {
                                 current_token_usage = token_usage;
                             }
                             LanguageModelCompletionEvent::Text(chunk) => {
+                                cx.emit(ThreadEvent::ReceivedTextChunk);
                                 if let Some(last_message) = thread.messages.last_mut() {
                                     if last_message.role == Role::Assistant {
                                         last_message.push_text(&chunk);
@@ -1780,7 +1781,7 @@ impl Thread {
                 thread_data,
                 final_project_snapshot
             );
-            client.telemetry().flush_events();
+            client.telemetry().flush_events().await;
 
             Ok(())
         })
@@ -1825,7 +1826,7 @@ impl Thread {
                     thread_data,
                     final_project_snapshot
                 );
-                client.telemetry().flush_events();
+                client.telemetry().flush_events().await;
 
                 Ok(())
             })
@@ -2081,7 +2082,7 @@ impl Thread {
                             github_login = github_login
                         );
 
-                        client.telemetry().flush_events();
+                        client.telemetry().flush_events().await;
                     }
                 }
             })
@@ -2199,6 +2200,7 @@ pub enum ThreadEvent {
     ShowError(ThreadError),
     UsageUpdated(RequestUsage),
     StreamedCompletion,
+    ReceivedTextChunk,
     StreamedAssistantText(MessageId, String),
     StreamedAssistantThinking(MessageId, String),
     StreamedToolUse {