[mcp] Support MCP Apps part 3 - Add mcp tool call support. (#17364)

- [x] Add a new app-server method so that MCP Apps can call their own
MCP server directly.

codex-rs/core/src/codex_thread.rs

@@ -9,6 +9,7 @@ use codex_protocol::config_types::Personality;
 use codex_protocol::config_types::ServiceTier;
 use codex_protocol::error::CodexErr;
 use codex_protocol::error::Result as CodexResult;
+use codex_protocol::mcp::CallToolResult;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseInputItem;
 use codex_protocol::models::ResponseItem;
@@ -224,6 +225,19 @@ impl CodexThread {
         Ok(serde_json::to_value(result)?)
     }
 
+    pub async fn call_mcp_tool(
+        &self,
+        server: &str,
+        tool: &str,
+        arguments: Option<serde_json::Value>,
+        meta: Option<serde_json::Value>,
+    ) -> anyhow::Result<CallToolResult> {
+        self.codex
+            .session
+            .call_tool(server, tool, arguments, meta)
+            .await
+    }
+
     pub fn enabled(&self, feature: Feature) -> bool {
         self.codex.enabled(feature)
     }