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/app-server-protocol/src/protocol/common.rs

@@ -311,6 +311,10 @@ client_request_definitions! {
         params: v2::ThreadShellCommandParams,
         response: v2::ThreadShellCommandResponse,
     },
+    ThreadApproveGuardianDeniedAction => "thread/approveGuardianDeniedAction" {
+        params: v2::ThreadApproveGuardianDeniedActionParams,
+        response: v2::ThreadApproveGuardianDeniedActionResponse,
+    },
     #[experimental("thread/backgroundTerminals/clean")]
     ThreadBackgroundTerminalsClean => "thread/backgroundTerminals/clean" {
         params: v2::ThreadBackgroundTerminalsCleanParams,

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -3639,6 +3639,20 @@ pub struct ThreadShellCommandParams {
 #[ts(export_to = "v2/")]
 pub struct ThreadShellCommandResponse {}
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadApproveGuardianDeniedActionParams {
+    pub thread_id: String,
+    /// Serialized `codex_protocol::protocol::GuardianAssessmentEvent`.
+    pub event: JsonValue,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadApproveGuardianDeniedActionResponse {}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]