Preserve voice meter history through quiet samples (#44928)

## Why

A quiet sample cleared all earlier activity from that channel's voice meter, making recent speech disappear immediately.

## What changed

Let quiet samples scroll into the microphone and speaker meter history so earlier activity remains visible until it ages out.

## Testing

Update history assertions and the meter snapshot to cover quiet samples on each channel and the eventual return to silence after a full history window.

GitOrigin-RevId: 834157df28c9d2cfbe9fa17bbfaf32b81313a295

codex-rs/tui/src/chatwidget/realtime/recording_controls.rs

@@ -222,15 +222,6 @@ impl ChatWidget {
             .audio_meter_history
             .iter()
             .any(|(microphone, speaker)| *microphone > 0 || *speaker > 0);
-        // Release a quiet channel instead of waiting for old peaks to scroll out.
-        for (microphone, speaker) in &mut self.realtime_conversation.audio_meter_history {
-            if microphone_intensity == 0 {
-                *microphone = 0;
-            }
-            if speaker_intensity == 0 {
-                *speaker = 0;
-            }
-        }
         if self.realtime_conversation.audio_meter_history.len() >= MAX_REALTIME_AUDIO_METER_FRAMES {
             self.realtime_conversation.audio_meter_history.pop_front();
         }

codex-rs/tui/src/chatwidget/realtime/recording_controls_tests.rs

@@ -266,7 +266,7 @@ async fn voice_meters_do_not_sample_again_on_early_redraws() {
             (119, 255)
         ])
     );
-    // Each channel settles on its first quiet sample, without clearing the other one.
+    // Quiet samples scroll into each channel without erasing earlier speech.
     for (elapsed_ms, peaks) in [(700, (0, 8192)), (800, (8192, 0))] {
         chat.refresh_realtime_audio_meters(
             now + std::time::Duration::from_millis(elapsed_ms),
@@ -274,6 +274,20 @@ async fn voice_meters_do_not_sample_again_on_early_redraws() {
         );
         meters.push(render_meter(&chat, /*width*/ 80));
     }
+    for frame in 0..super::super::MAX_REALTIME_AUDIO_METER_FRAMES {
+        chat.refresh_realtime_audio_meters(
+            now + std::time::Duration::from_millis(900 + frame as u64 * 100),
+            || (0, 0),
+        );
+        if frame == 0 {
+            meters.push(render_meter(&chat, /*width*/ 80));
+        }
+    }
+    assert_eq!(
+        chat.realtime_conversation.audio_meter_history,
+        std::collections::VecDeque::from([(0, 0); super::super::MAX_REALTIME_AUDIO_METER_FRAMES])
+    );
+    meters.push(render_meter(&chat, /*width*/ 80));
     insta::assert_snapshot!(meters.join("\n"));
 }
 
@@ -287,7 +301,7 @@ async fn voice_meters_preserve_silence_and_restart_sampling_after_reset() {
     chat.refresh_realtime_audio_meters(now + std::time::Duration::from_secs(1), || (0, 0));
     assert_eq!(
         chat.realtime_conversation.audio_meter_history,
-        std::collections::VecDeque::from([(0, 0), (0, 0)])
+        std::collections::VecDeque::from([(255, 119), (0, 0)])
     );
     chat.reset_realtime_conversation();
     activate_voice(&mut chat);

codex-rs/tui/src/chatwidget/realtime/snapshots/codex_tui__chatwidget__realtime__tests__recording_controls_tests__voice_meters_do_not_sample_again_on_early_redraws.snap

@@ -1,8 +1,11 @@
 ---
 source: tui/src/chatwidget/realtime/recording_controls_tests.rs
+assertion_line: 291
 expression: "meters.join(\"\\n\")"
 ---
 mic ██████  codex ▅▅▅▅▅▅
 mic ██████  codex ▅▅▅▅▅▅
-mic ▁▁▁▁▁▁  codex ▅▅▅▅██
-mic ▁▁▁▁▁█  codex ▁▁▁▁▁▁
+mic ████▅▁  codex ▅▅▅▅██
+mic ███▅▁█  codex ▅▅▅██▁
+mic ██▅▁█▁  codex ▅▅██▁▁
+mic ▁▁▁▁▁▁  codex ▁▁▁▁▁▁