[mcp] Support server-driven elicitations (#17043)

- [x] Enables MCP elicitation for custom servers, not just Codex Apps
- [x] Adds an RMCP service wrapper to preserve elicitation _meta
- [x] Round-trips response _meta for persist/approval choices
- [x] Updates TUI empty-schema elicitations into message-only approval
prompts

codex-rs/codex-mcp/src/mcp_connection_manager.rs

@@ -1319,19 +1319,15 @@ impl From<anyhow::Error> for StartupOutcomeError {
     }
 }
 
-fn elicitation_capability_for_server(server_name: &str) -> Option<ElicitationCapability> {
-    if server_name == CODEX_APPS_MCP_SERVER_NAME {
-        // https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation#capabilities
-        // indicates this should be an empty object.
-        Some(ElicitationCapability {
-            form: Some(FormElicitationCapability {
-                schema_validation: None,
-            }),
-            url: None,
-        })
-    } else {
-        None
-    }
+fn elicitation_capability_for_server(_server_name: &str) -> Option<ElicitationCapability> {
+    // https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation#capabilities
+    // indicates this should be an empty object.
+    Some(ElicitationCapability {
+        form: Some(FormElicitationCapability {
+            schema_validation: None,
+        }),
+        url: None,
+    })
 }
 
 async fn start_server_task(

codex-rs/codex-mcp/src/mcp_connection_manager_tests.rs

@@ -508,19 +508,19 @@ async fn list_all_tools_uses_startup_snapshot_when_client_startup_fails() {
 }
 
 #[test]
-fn elicitation_capability_enabled_only_for_codex_apps() {
-    let codex_apps_capability = elicitation_capability_for_server(CODEX_APPS_MCP_SERVER_NAME);
-    assert!(matches!(
-        codex_apps_capability,
-        Some(ElicitationCapability {
-            form: Some(FormElicitationCapability {
-                schema_validation: None
-            }),
-            url: None,
-        })
-    ));
-
-    assert!(elicitation_capability_for_server("custom_mcp").is_none());
+fn elicitation_capability_enabled_for_custom_servers() {
+    for server_name in [CODEX_APPS_MCP_SERVER_NAME, "custom_mcp"] {
+        let capability = elicitation_capability_for_server(server_name);
+        assert!(matches!(
+            capability,
+            Some(ElicitationCapability {
+                form: Some(FormElicitationCapability {
+                    schema_validation: None
+                }),
+                url: None,
+            })
+        ));
+    }
 }
 
 #[test]