feat(topbar): the recording lives in the pill — green pulse, REC clock, Stop Recording

Build 730 (creator):

- Left pill while recording: solid #2ECC71 dot pulsing 1.0 <-> 0.2 on the existing one-second timer, and
  "REC: hh:mm:ss" in Consolas so the digits cannot jitter the pill's width. Idle face unchanged.
- Right pill while recording: a stop square and "Stop Recording"; clicking it runs the normal stop, which
  halts and resets the clock and returns the pair to "Local MP4" / "Start Recording".
- The separate reality line (dot + REC/LIVE + elapsed + End) is now LIVE-ONLY: a recording would otherwise
  print the same three facts twice. RunningVisible is IsLive, and ShowOutputStage no longer hides itself
  for a recording (it must be on screen to carry the clock and the stop).

Two rules collided and are now separated rather than merged: a creator's Stop on a recording restores the
Local MP4 pair (build 730), while a pipeline FAILURE still clears both pills (the 2026-09-01 zombie rule).
StopStream(afterFailure:) carries the difference, and the pump-failure path passes it.

RealAppHost.Run was rethrowing with `throw failure;`, which destroyed the original stack — a failing
assertion inside the action reported the wrapper's line instead of its own. ExceptionDispatchInfo now
preserves it; that is how the two failures above were located in one pass instead of five.

680 pass (one audio-pipe instance flake under full-suite load, passes alone), 0 warnings.
Scope justification: Assets/starting-background.jpg is outside this unit — the creator's replacement art,
still awaiting their visual check.

Controls/TopBar.xaml

@@ -135,11 +135,27 @@
                                     Command="{Binding SelectLocalMp4Command}"
                                     Visibility="{Binding LocalMp4ChipVisible, Converter={StaticResource BoolToVis}}"
                                     ToolTip="Record to a local MP4">
-                                <StackPanel Orientation="Horizontal">
-                                    <Path Style="{StaticResource OutputChipIcon}" Tag="{Binding RecordPillOn}" Data="M12,2a10,10 0 1,0 0,20a10,10 0 1,0 0,-20zM12,4a8,8 0 1,1 0,16a8,8 0 1,1 0,-16zM12,7.5a4.5,4.5 0 1,1 0,9a4.5,4.5 0 1,1 0,-9z"/>
-                                    <TextBlock Text="Local MP4" FontSize="12" Margin="6,0,0,0" VerticalAlignment="Center"
-                                               Foreground="{Binding Foreground, RelativeSource={RelativeSource AncestorType=Button}}"/>
-                                </StackPanel>
+                                <Grid>
+                                    <!-- Idle face: the record glyph and the output's name. -->
+                                    <StackPanel Orientation="Horizontal"
+                                                Visibility="{Binding IsRecording, Converter={StaticResource InverseBoolToVis}}">
+                                        <Path Style="{StaticResource OutputChipIcon}" Tag="{Binding RecordPillOn}" Data="M12,2a10,10 0 1,0 0,20a10,10 0 1,0 0,-20zM12,4a8,8 0 1,1 0,16a8,8 0 1,1 0,-16zM12,7.5a4.5,4.5 0 1,1 0,9a4.5,4.5 0 1,1 0,-9z"/>
+                                        <TextBlock Text="Local MP4" FontSize="12" Margin="6,0,0,0" VerticalAlignment="Center"
+                                                   Foreground="{Binding Foreground, RelativeSource={RelativeSource AncestorType=Button}}"/>
+                                    </StackPanel>
+                                    <!-- Recording face: solid green dot pulsing once a second, and a tabular
+                                         clock so the pill does not jitter as the digits change. -->
+                                    <StackPanel Orientation="Horizontal"
+                                                Visibility="{Binding IsRecording, Converter={StaticResource BoolToVis}}">
+                                        <Ellipse Width="10" Height="10" VerticalAlignment="Center"
+                                                 Fill="{StaticResource Brush.RecordLive}"
+                                                 Opacity="{Binding RecDotOpacity, Mode=OneWay}"/>
+                                        <TextBlock Text="{Binding RecordChipText}" FontSize="12" FontWeight="Bold"
+                                                   Margin="6,0,0,0" VerticalAlignment="Center"
+                                                   FontFamily="Consolas"
+                                                   Foreground="{Binding Foreground, RelativeSource={RelativeSource AncestorType=Button}}"/>
+                                    </StackPanel>
+                                </Grid>
                             </Button>
                             <!-- YouTube's two actions: the real stream and the private (test) one. -->
                             <Button Style="{StaticResource OutputChip}" Command="{Binding GoLiveCommand}"
@@ -173,7 +189,7 @@
                                     Visibility="{Binding ShowEndRecordingAction, Converter={StaticResource BoolToVis}}">
                                 <StackPanel Orientation="Horizontal">
                                     <Path Style="{StaticResource OutputChipIcon}" Data="M6,6h12v12H6z"/>
-                                    <TextBlock Text="End Recording" FontSize="12" Margin="6,0,0,0" VerticalAlignment="Center"
+                                    <TextBlock Text="Stop Recording" FontSize="12" Margin="6,0,0,0" VerticalAlignment="Center"
                                                Foreground="{StaticResource Brush.SegmentTextInactive}"/>
                                 </StackPanel>
                             </Button>