Add plumbing to approve stored Auto-Review denials (#18955)

## Summary

This adds the structural plumbing needed for an app-server client to
approve a previously denied Guardian review and carry that approval
context into the next model turn.

This PR does not add the actual `/auto-review-denials` tool 

## What Changed

- Added app-server v2 RPC `thread/approveGuardianDeniedAction`.
- Added generated JSON schema and TypeScript fixtures for
`ThreadApproveGuardianDeniedAction*`.
- Added core `Op::ApproveGuardianDeniedAction`.
- Added a core handler that validates the event is a denied Guardian
assessment and injects a developer message containing the stored denial
event JSON.
- Queues the approval context for the next turn if there is no active
turn yet.
- Added the TUI app-server bridge so `Op::ApproveGuardianDeniedAction {
event }` is routed to the app-server request.

## What This Does Not Do

- Does not add `/auto-review-denials`.
- Does not add chat widget recent-denial state.
- Does not add popup/list UI.
- Does not add a product-facing denial lookup/store.
- Does not change where Guardian denials are originally emitted or
persisted.

## Verification

- `cargo test -p codex-tui thread_approve_guardian_denied_action`

codex-rs/core/src/session/mod.rs

@@ -3043,7 +3043,6 @@ impl Session {
     }
 
     /// Queue response items to be injected into the next active turn created for this session.
-    #[cfg(test)]
     pub(crate) async fn queue_response_items_for_next_turn(&self, items: Vec<ResponseInputItem>) {
         if items.is_empty() {
             return;