Update guardian output schema (#17061)

## Summary
- Update guardian output schema to separate risk, authorization,
outcome, and rationale.
- Feed guardian rationale into rejection messages.
- Split the guardian policy into template and tenant-config sections.

## Validation
- `cargo test -p codex-core mcp_tool_call`
- `env -u CODEX_SANDBOX_NETWORK_DISABLED INSTA_UPDATE=always cargo test
-p codex-core guardian::`

---------

Co-authored-by: Owen Lin <owen@openai.com>

codex-rs/core/src/codex_tests.rs

@@ -2884,6 +2884,7 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
         session_telemetry: session_telemetry.clone(),
         models_manager: Arc::clone(&models_manager),
         tool_approvals: Mutex::new(ApprovalStore::default()),
+        guardian_rejection_rationales: Mutex::new(std::collections::HashMap::new()),
         skills_manager,
         plugins_manager,
         mcp_manager,
@@ -3726,6 +3727,7 @@ pub(crate) async fn make_session_and_context_with_dynamic_tools_and_rx(
         session_telemetry: session_telemetry.clone(),
         models_manager: Arc::clone(&models_manager),
         tool_approvals: Mutex::new(ApprovalStore::default()),
+        guardian_rejection_rationales: Mutex::new(std::collections::HashMap::new()),
         skills_manager,
         plugins_manager,
         mcp_manager,