Route Codex Apps MCP through plugin service (#34389)

## What changed

- Point the default Codex Apps MCP server at `ps/mcp` instead of the legacy Apps endpoint for both `backend-api` and `api/codex` base URLs.
- Use the same server configuration for Codex Apps and the hosted plugin runtime.
- Update MCP integration tests and test-server routing to expect the plugin-service path.

GitOrigin-RevId: 939f20dcff67ba6f79c11b328bfc624b25e3aac2

codex-rs/codex-mcp/src/mcp/mod.rs

@@ -475,14 +475,12 @@ fn normalize_codex_apps_base_url(base_url: &str) -> String {
 
 fn codex_apps_mcp_url_for_base_url(base_url: &str) -> String {
     let base_url = normalize_codex_apps_base_url(base_url);
-    let (base_url, default_path) = if base_url.contains("/backend-api") {
-        (base_url, "wham/apps")
-    } else if base_url.contains("/api/codex") {
-        (base_url, "apps")
+    let base_url = if base_url.contains("/backend-api") || base_url.contains("/api/codex") {
+        base_url
     } else {
-        (format!("{base_url}/api/codex"), "apps")
+        format!("{base_url}/api/codex")
     };
-    format!("{base_url}/{default_path}")
+    format!("{base_url}/ps/mcp")
 }
 
 pub fn codex_apps_mcp_server_config(
@@ -504,18 +502,7 @@ pub fn hosted_plugin_runtime_mcp_server_config(
     apps_mcp_product_sku: Option<&str>,
     originator: Option<&str>,
 ) -> McpServerConfig {
-    let base_url = normalize_codex_apps_base_url(chatgpt_base_url);
-    let base_url = if base_url.contains("/backend-api") || base_url.contains("/api/codex") {
-        base_url
-    } else {
-        format!("{base_url}/api/codex")
-    };
-    mcp_server_config_for_url(
-        format!("{base_url}/ps/mcp"),
-        apps_mcp_product_sku,
-        originator,
-        McpServerAuth::ChatGpt,
-    )
+    codex_apps_mcp_server_config(chatgpt_base_url, apps_mcp_product_sku, originator)
 }
 
 fn mcp_server_config_for_url(