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/protocol/src/protocol.rs

@@ -701,6 +701,9 @@ pub enum Op {
     /// Request a code review from the agent.
     Review { review_request: ReviewRequest },
 
+    /// Record that the user approved one retry of a concrete Guardian-denied action.
+    ApproveGuardianDeniedAction { event: GuardianAssessmentEvent },
+
     /// Request to shut down codex instance.
     Shutdown,
 
@@ -820,6 +823,7 @@ impl Op {
             Self::Undo => "undo",
             Self::ThreadRollback { .. } => "thread_rollback",
             Self::Review { .. } => "review",
+            Self::ApproveGuardianDeniedAction { .. } => "approve_guardian_denied_action",
             Self::Shutdown => "shutdown",
             Self::RunUserShellCommand { .. } => "run_user_shell_command",
             Self::ListModels => "list_models",