Stop TUI chats on misalignment policy violations (#39261)

## Why

When the app server reports a misalignment policy violation, the TUI must stop the affected chat rather than allow more work to continue in it.

## What changed

- Finalize the active turn, clear queued and draft input, disable the composer, and reject further operations and interactive requests for the stopped chat.
- Interrupt an active side conversation when its parent reports the violation, and prevent queued turns, forks, approvals, or goal resumption from restarting work.
- Show a non-dismissible precaution view that directs users to start a new chat or resume another one, with agent command center navigation for remote sessions.

## Testing

Added coverage for stopped-chat behavior, parent/side-thread handling, blocked goal resumption, navigation actions, and narrow and remote-session rendering.

GitOrigin-RevId: 0268c46a19294a17765ea4099f389f15ffaaf030

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

@@ -13,6 +13,7 @@ use crate::config_update::format_config_error;
 use crate::external_agent_config_migration::flow::ExternalAgentConfigMigrationFlowOutcome;
 use crate::pager_overlay::TranscriptHistoryState;
 use crate::session_resume::cwds_differ;
+use codex_app_server_protocol::ThreadGoalStatus;
 #[cfg(target_os = "windows")]
 use codex_config::types::WindowsSandboxModeToml;
 
@@ -25,6 +26,24 @@ impl App {
         app_server: &mut AppServerSession,
         event: AppEvent,
     ) -> Result<AppRunControl> {
+        if self.chat_widget.has_misalignment_policy_violation()
+            && matches!(
+                event,
+                AppEvent::OpenAgentPicker
+                    | AppEvent::SelectAgentThread(_)
+                    | AppEvent::StartSide { .. }
+                    | AppEvent::ForkCurrentSession { .. }
+                    | AppEvent::ForkSessionForPromptEdit { .. }
+                    | AppEvent::SetThreadGoalDraft { .. }
+                    | AppEvent::SetThreadGoalStatus {
+                        status: ThreadGoalStatus::Active,
+                        ..
+                    }
+            )
+        {
+            return Ok(AppRunControl::Continue);
+        }
+
         match event {
             AppEvent::SkillsListLoaded { ref cwd, .. }
             | AppEvent::PluginMentionsLoaded { ref cwd, .. }
@@ -35,6 +54,9 @@ impl App {
                     /*initial_user_message*/ None, name,
                 )
                 .await;
+                if self.chat_widget.has_misalignment_policy_violation() {
+                    self.chat_widget.show_misalignment_policy_precaution();
+                }
             }
             AppEvent::ChangeWorkingDirectory {
                 thread_id,