Expose app-server diagnostics through the experimental API (#37470)

## What changed

- Add the experimental `server/diagnostics` request, returning the app-server process ID, resident memory, platform-dependent physical footprint, and registered diagnostic gauges.
- Export the new protocol types in the generated JSON and TypeScript schemas and document the request.

## Testing

- Verify the response includes process measurements and the registered live-thread gauge.
- Verify the request is rejected unless `capabilities.experimentalApi` is enabled.

GitOrigin-RevId: 099d60a9c421a74ff1a72fe524e0dfeb89cf1057

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -478,6 +478,14 @@ client_request_definitions! {
         response: v1::InitializeResponse,
     },
 
+    #[experimental("server/diagnostics")]
+    /// Read content-free, process-local diagnostics.
+    ServerDiagnostics => "server/diagnostics" {
+        params: v2::ServerDiagnosticsParams,
+        serialization: None,
+        response: v2::ServerDiagnosticsResponse,
+    },
+
     /// NEW APIs
     // Thread lifecycle
     // Uses `inspect_params` because only some fields are experimental.

codex-rs/app-server-protocol/src/protocol/v2/diagnostics.rs

@@ -0,0 +1,37 @@
+use crate::JsonSchema;
+use crate::TS;
+use serde::Deserialize;
+use serde::Serialize;
+
+#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ServerDiagnosticsParams {}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ServerDiagnosticsResponse {
+    pub process: ServerDiagnosticsProcess,
+    pub gauges: Vec<ServerDiagnosticsGauge>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ServerDiagnosticsProcess {
+    pub id: u32,
+    #[ts(type = "number | null")]
+    pub resident_memory_bytes: Option<u64>,
+    #[ts(type = "number | null")]
+    pub physical_footprint_bytes: Option<u64>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ServerDiagnosticsGauge {
+    pub name: String,
+    #[ts(type = "number")]
+    pub value: u64,
+}

codex-rs/app-server-protocol/src/protocol/v2/mod.rs

@@ -7,6 +7,7 @@ mod collaboration_mode;
 mod command_exec;
 mod config;
 mod current_time;
+mod diagnostics;
 mod environment;
 mod experimental_feature;
 mod feedback;
@@ -35,6 +36,7 @@ pub use collaboration_mode::*;
 pub use command_exec::*;
 pub use config::*;
 pub use current_time::*;
+pub use diagnostics::*;
 pub use environment::*;
 pub use experimental_feature::*;
 pub use feedback::*;