TUI: Remove core protocol dependency [3/7] (#20174)

## Why

This is part 3 of a 7-PR stack to remove direct
`codex_protocol::protocol` usage from `codex-tui` while keeping each
layer reviewable and shippable.

With `AppCommand` now explicit, the internal app event bus can carry TUI
commands directly instead of bouncing through core `Op` values.

## What changed

- Changed `AppEvent::CodexOp` and `AppEvent::SubmitThreadOp` to carry
`AppCommand`.
- Updated app-event senders and direct emitters to submit `AppCommand`
values.
- Adjusted tests to match `AppCommand` or convert back through
`into_core()` where they intentionally assert legacy payload equality.

## Verification

- `cargo test -p codex-tui --no-run`

codex-rs/tui/src/app/config_persistence.rs

@@ -351,8 +351,8 @@ impl App {
             #[cfg(target_os = "windows")]
             {
                 let windows_sandbox_level = WindowsSandboxLevel::from_config(&self.config);
-                self.app_event_tx.send(AppEvent::CodexOp(
-                    AppCommand::override_turn_context(
+                self.app_event_tx
+                    .send(AppEvent::CodexOp(AppCommand::override_turn_context(
                         /*cwd*/ None,
                         /*approval_policy*/ None,
                         /*approvals_reviewer*/ None,
@@ -365,9 +365,7 @@ impl App {
                         /*service_tier*/ None,
                         /*collaboration_mode*/ None,
                         /*personality*/ None,
-                    )
-                    .into_core(),
-                ));
+                    )));
             }
         }
 

codex-rs/tui/src/app/event_dispatch.rs

@@ -313,15 +313,14 @@ impl App {
                 return Ok(AppRunControl::Exit(ExitReason::Fatal(message)));
             }
             AppEvent::CodexOp(op) => {
-                self.submit_active_thread_op(app_server, op.into()).await?;
+                self.submit_active_thread_op(app_server, op).await?;
             }
             AppEvent::ApproveRecentAutoReviewDenial { thread_id, id } => {
                 self.chat_widget
                     .approve_recent_auto_review_denial(thread_id, id);
             }
             AppEvent::SubmitThreadOp { thread_id, op } => {
-                self.submit_thread_op(app_server, thread_id, op.into())
-                    .await?;
+                self.submit_thread_op(app_server, thread_id, op).await?;
             }
             AppEvent::ThreadHistoryEntryResponse { thread_id, event } => {
                 self.enqueue_thread_history_entry_response(thread_id, event)
@@ -989,8 +988,7 @@ impl App {
                                         /*service_tier*/ None,
                                         /*collaboration_mode*/ None,
                                         /*personality*/ None,
-                                    )
-                                    .into(),
+                                    ),
                                 ));
                                 self.app_event_tx.send(
                                     AppEvent::OpenWorldWritableWarningConfirmation {
@@ -1015,8 +1013,7 @@ impl App {
                                         /*service_tier*/ None,
                                         /*collaboration_mode*/ None,
                                         /*personality*/ None,
-                                    )
-                                    .into(),
+                                    ),
                                 ));
                                 self.app_event_tx
                                     .send(AppEvent::UpdateAskForApprovalPolicy(preset.approval));

codex-rs/tui/src/app/tests.rs

@@ -6,6 +6,7 @@ use super::*;
 use crate::app_backtrack::BacktrackSelection;
 use crate::app_backtrack::BacktrackState;
 use crate::app_backtrack::user_count;
+use crate::app_command::AppCommand;
 
 use crate::chatwidget::ChatWidgetInit;
 use crate::chatwidget::create_initial_user_message;
@@ -441,12 +442,12 @@ async fn enqueue_primary_thread_session_replays_turns_before_initial_prompt_subm
             }
             AppEvent::SubmitThreadOp {
                 thread_id: op_thread_id,
-                op: Op::UserTurn { items, .. },
+                op: AppCommand::UserTurn { items, .. },
             } => {
                 assert_eq!(op_thread_id, thread_id);
                 submitted_items = Some(items);
             }
-            AppEvent::CodexOp(Op::UserTurn { items, .. }) => {
+            AppEvent::CodexOp(AppCommand::UserTurn { items, .. }) => {
                 submitted_items = Some(items);
             }
             _ => {}

codex-rs/tui/src/app/thread_routing.rs

@@ -706,7 +706,8 @@ impl App {
                 Ok(true)
             }
             AppCommandView::OverrideTurnContext { .. } => Ok(true),
-            AppCommandView::Other(Op::ApproveGuardianDeniedAction { event }) => {
+            AppCommandView::ApproveGuardianDeniedAction { event }
+            | AppCommandView::Other(Op::ApproveGuardianDeniedAction { event }) => {
                 app_server
                     .thread_approve_guardian_denied_action(thread_id, event)
                     .await?;