fix(app-server): add duration_ms to McpToolCallItem (#7605)

Seems like a nice field to have, and also VSCE does render this one.

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

@@ -1141,6 +1141,9 @@ pub enum ThreadItem {
         arguments: JsonValue,
         result: Option<McpToolCallResult>,
         error: Option<McpToolCallError>,
+        /// The duration of the MCP tool call in milliseconds.
+        #[ts(type = "number | null")]
+        duration_ms: Option<i64>,
     },
     #[serde(rename_all = "camelCase")]
     #[ts(rename_all = "camelCase")]