TASK 18: local (record-only) recording pipeline + top-bar pills/light/Start-End button UX

Encoder dual-output: StreamEnabled/RecordEnabled/RecordPath options; per-output
ffmpeg block (stream ->flv, record ->mp4); throw unless at least one output.

RecordingFile: auto-name ty-<yyyymmdd>-<start hhmm>-0000.mp4, rename-on-stop to
ty-...-<len hhmmss>.mp4 with numeric-suffix on collision. LayoutStore persists
record folder. MainViewModel: REC/ON-AIR pills, status light, single Start<->End
button (replaces Start/Stop variants), StopStream no longer signs out, explicit
session timer. About overlay widened. Sign In label + spacing before Start.

Tests: 244 passed / 246 (2 pre-existing: AudioPipeline gains-mute, RoundClip).
Build 0 warnings. Scope check clean.

Memory-map correction (derived-solution rule, 2026-08-29): image-shrink recipe was
never recorded when first done, so it was re-derived. Added Derived-solution/recipes
rule to AGENTS.md; MyMistakes.md now a permanent recipes registry (records the
verified WPF-imaging shrink recipe); schema.md rows MyMistakes as registry; ai.md
points to the rule. README hero image replaced: 3.2MB screenshot -> 1400x794 ->
188KB docs/ytLlive-preview.jpg (JPEG q82).

ytLive.Tests/FfmpegEncoderTests.cs

@@ -175,6 +175,56 @@ public class FfmpegEncoderTests
         await Assert.ThrowsAsync<ArgumentException>(() => encoder.StartAsync(new EncoderOptions()));
     }
 
+    [Fact]
+    public void Args_RecordOnly_SkipsRtmp_WritesMp4()
+    {
+        var args = FfmpegArgs.Build(
+            new EncoderOptions
+            {
+                StreamEnabled = false,
+                RecordEnabled = true,
+                RecordPath = @"C:\videos\ty-20260829-1405-0000.mp4",
+                Width = 1920,
+                Height = 1080,
+                Fps = 60,
+                BitrateKbps = 8000,
+            },
+            "libopenh264").ToArray();
+
+        Assert.DoesNotContain("flv", args);
+        Assert.DoesNotContain("rtmp", args);
+        var idx = Array.IndexOf(args, "mp4");
+        Assert.True(idx > -1, "record-only must emit a -f mp4 output");
+        Assert.Equal("-f", args[idx - 1]);
+        Assert.Equal(@"C:\videos\ty-20260829-1405-0000.mp4", args[idx + 1]);
+    }
+
+    [Fact]
+    public void Args_DualOutput_HasTwoMapBlocks_FlvAndMp4()
+    {
+        var args = FfmpegArgs.Build(
+            new EncoderOptions
+            {
+                RtmpUrl = "rtmp://a.rtmp.youtube.com/live2/key",
+                StreamEnabled = true,
+                RecordEnabled = true,
+                RecordPath = @"C:\videos\ty-20260829-1405-0000.mp4",
+                Width = 1280,
+                Height = 720,
+                Fps = 30,
+                BitrateKbps = 4000,
+            },
+            "h264_nvenc").ToArray();
+
+        // two video maps (one per output block)
+        Assert.Equal(2, args.Count(a => a == "0:v"));
+        Assert.Equal(2, args.Count(a => a == "-c:v"));
+        Assert.Contains("flv", args);
+        Assert.Contains("mp4", args);
+        Assert.Contains("rtmp://a.rtmp.youtube.com/live2/key", args);
+        Assert.Contains(@"C:\videos\ty-20260829-1405-0000.mp4", args);
+    }
+
     [Fact]
     public async Task SubmitFrame_WhenNotRunning_Throws()
     {

ytLive.Tests/FramePumpTests.cs

@@ -196,7 +196,7 @@ public class FramePumpTests
 
         Assert.False(pump.IsRunning);
         Assert.Equal(0, encoder.StartCount);
-        Assert.Contains(log, m => m.Contains("RTMP"));
+        Assert.Contains(log, m => m.Contains("no output configured"));
 
         await pump.StopAsync(); // no-op after a skipped start
         Assert.Equal(0, encoder.StopCount);

ytLive.Tests/RecordingFileTests.cs

@@ -0,0 +1,49 @@
+using Xunit;
+using ytLive.Services;
+
+namespace ytLive.Tests;
+
+/// <summary>
+/// Local recording filename rules (TASK 18): <c>ty-&lt;yyyyMMdd&gt;-&lt;HHmm start&gt;-&lt;hh2mm2 length&gt;.mp4</c>.
+/// Recordings start with a <c>0000</c> length placeholder and are renamed on stop.
+/// </summary>
+public class RecordingFileTests
+{
+    [Fact]
+    public void BuildStartName_UsesDateHourAndMinute_WithZeroLength()
+    {
+        var start = new DateTime(2026, 8, 29, 14, 5, 0);
+        Assert.Equal("ty-20260829-1405-0000", RecordingFile.BuildStartName(start));
+    }
+
+    [Fact]
+    public void BuildStartName_PadsSingleDigitHourAndMinute()
+    {
+        var start = new DateTime(2026, 1, 2, 9, 7, 0);
+        Assert.Equal("ty-20260102-0907-0000", RecordingFile.BuildStartName(start));
+    }
+
+    [Fact]
+    public void BuildFinalName_ShortRecording_IsHhmmOfLength()
+    {
+        var start = new DateTime(2026, 8, 29, 14, 5, 0);
+        var length = TimeSpan.FromMinutes(2);
+        Assert.Equal("ty-20260829-1405-0002", RecordingFile.BuildFinalName(start, length));
+    }
+
+    [Fact]
+    public void BuildFinalName_HourAndMinutes_ConcatenatesHh2Mm2()
+    {
+        var start = new DateTime(2026, 8, 29, 14, 5, 0);
+        var length = new TimeSpan(1, 15, 0); // 1h 15m
+        Assert.Equal("ty-20260829-1405-0115", RecordingFile.BuildFinalName(start, length));
+    }
+
+    [Fact]
+    public void BuildFinalName_OverFlowHours_ShowsTotalHours()
+    {
+        var start = new DateTime(2026, 8, 29, 14, 5, 0);
+        var length = new TimeSpan(12, 30, 0); // 12h 30m
+        Assert.Equal("ty-20260829-1405-1230", RecordingFile.BuildFinalName(start, length));
+    }
+}