feat(tui): Add confirmation prompt for enabling full access approvals (#4980)

## Summary
Adds a confirmation screen when a user attempts to select Full Access
via the `/approvals` flow in the TUI.

If the user selects the remember option, the preference is persisted to
config.toml as `full_access_warning_acknowledged`, so they will not be
prompted again.


## Testing
- [x] Adds snapshot test coverage for the approvals flow and the
confirmation flow
<img width="865" height="187" alt="Screenshot 2025-10-08 at 6 04 59 PM"
src="https://github.com/user-attachments/assets/fd1dac62-28b0-4835-ba91-5da6dc5ec4c4"
/>



------
https://chatgpt.com/codex/tasks/task_i_68e6c5c458088322a28efa3207058180

---------

Co-authored-by: Fouad Matin <169186268+fouad-openai@users.noreply.github.com>
Co-authored-by: Fouad Matin <fouad@openai.com>

codex-rs/tui/src/app_event.rs

@@ -1,5 +1,6 @@
 use std::path::PathBuf;
 
+use codex_common::approval_presets::ApprovalPreset;
 use codex_common::model_presets::ModelPreset;
 use codex_core::protocol::ConversationPathResponseEvent;
 use codex_core::protocol::Event;
@@ -67,12 +68,26 @@ pub(crate) enum AppEvent {
         presets: Vec<ModelPreset>,
     },
 
+    /// Open the confirmation prompt before enabling full access mode.
+    OpenFullAccessConfirmation {
+        preset: ApprovalPreset,
+    },
+
     /// Update the current approval policy in the running app and widget.
     UpdateAskForApprovalPolicy(AskForApproval),
 
     /// Update the current sandbox policy in the running app and widget.
     UpdateSandboxPolicy(SandboxPolicy),
 
+    /// Update whether the full access warning prompt has been acknowledged.
+    UpdateFullAccessWarningAcknowledged(bool),
+
+    /// Persist the acknowledgement flag for the full access warning prompt.
+    PersistFullAccessWarningAcknowledged,
+
+    /// Re-open the approval presets popup.
+    OpenApprovalsPopup,
+
     /// Forwarded conversation history snapshot from the current conversation.
     ConversationHistory(ConversationPathResponseEvent),