Report the exec-server release version in environment info (#42270)

## Why

Clients need the executor's release version to make version-based compatibility decisions.

## What changed

- Add `executorVersion` to `EnvironmentInfo` and return it from both `initialize` and `environment/info`.
- Resolve the package release version at process startup so the advertised value remains stable for the server's lifetime.
- Use `0.0.0` when the version is unknown or omitted by a legacy executor.

## Testing

- Cover packaged and source-build initialization, startup caching, protocol serialization, and client-side metadata caching.

GitOrigin-RevId: a0c7f0b701a8e7e50345cd5fb1b5c5d2d38ff3b1

codex-rs/exec-server/src/server/handler.rs

@@ -158,7 +158,7 @@ impl ExecServerHandler {
             .unwrap_or_else(std::sync::PoisonError::into_inner) = Some(session);
         Ok(InitializeResponse {
             session_id,
-            environment_info: Some(EnvironmentInfo::local()),
+            environment_info: Some(super::release_version::local_environment_info()),
         })
     }
 
@@ -179,7 +179,7 @@ impl ExecServerHandler {
 
     pub(crate) fn environment_info(&self) -> Result<EnvironmentInfo, JSONRPCErrorError> {
         self.require_initialized_for("environment info")?;
-        Ok(EnvironmentInfo::local())
+        Ok(super::release_version::local_environment_info())
     }
 
     pub(crate) async fn environment_config_read(