Remove TUI realtime voice support (#27801)

## Why

Removes the realtime audio support from TUI.

## What Changed

- Removed the TUI `/realtime` and realtime `/settings` command paths.
- Deleted TUI voice capture/playback, WebRTC session handling,
audio-device selection UI, and recording-meter code.
- Removed TUI realtime tests and snapshots that covered the deleted
surfaces.
- Dropped the TUI-only `cpal` and `codex-realtime-webrtc` dependencies
and refreshed the Rust/Bazel locks.

codex-rs/tui/src/chatwidget/slash_dispatch.rs

@@ -261,22 +261,6 @@ impl ChatWidget {
             SlashCommand::Model => {
                 self.open_model_popup();
             }
-            SlashCommand::Realtime => {
-                if !self.realtime_conversation_enabled() {
-                    return;
-                }
-                if self.realtime_conversation.is_live() {
-                    self.stop_realtime_conversation_from_ui();
-                } else {
-                    self.start_realtime_conversation();
-                }
-            }
-            SlashCommand::Settings => {
-                if !self.realtime_audio_device_selection_enabled() {
-                    return;
-                }
-                self.open_realtime_audio_popup();
-            }
             SlashCommand::Personality => {
                 self.open_personality_popup();
             }
@@ -962,8 +946,6 @@ impl ChatWidget {
             goal_command_enabled: self.config.features.enabled(Feature::Goals),
             service_tier_commands_enabled: self.fast_mode_enabled(),
             personality_command_enabled: self.config.features.enabled(Feature::Personality),
-            realtime_conversation_enabled: self.realtime_conversation_enabled(),
-            audio_device_selection_enabled: self.realtime_audio_device_selection_enabled(),
             allow_elevate_sandbox,
             side_conversation_active: self.active_side_conversation,
         }
@@ -1003,8 +985,6 @@ impl ChatWidget {
             | SlashCommand::Compact
             | SlashCommand::Review
             | SlashCommand::Model
-            | SlashCommand::Realtime
-            | SlashCommand::Settings
             | SlashCommand::Personality
             | SlashCommand::Plan
             | SlashCommand::Goal