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/telemetry_events/src/telemetry_events.rs

@@ -15,6 +15,7 @@ pub struct EventRequestBody {
     pub session_id: Option<String>,
     pub metrics_id: Option<String>,
     /// True for Zed staff, otherwise false
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub is_staff: Option<bool>,
     /// Zed version number
     pub app_version: String,