v5 pre-release: multi-track drift fix, more self-tests, logging, CLI, version bump

Multi-track recording drift fix (Ed's question — can the separate tracks drift over an hour?):
 * Root: FlushPeerTracks skipped a peer that produced no samples in a render block, so a peer that
   went quiet long enough for its session to be pruned (>4 s idle) would have its track fall behind
   and desync. Now every peer track is padded to a full render block each cycle (silence when the
   peer produced nothing), so all peer tracks stay sample-locked to the single render clock — they
   can't drift apart however long the recording runs, and all end the same length. Same padding for
   the single-file bypass path. OnRecordBlockComplete now carries the block's float count.
   (The peer tracks are already resampled to the render clock per peer, so this makes peer-to-peer
   sync exact; your own "me" track is capture-clocked — same soundcard for capture+playback = same
   clock = no drift, different interfaces can drift slightly.)

 * Self-test: two new steps — "Per-peer shaping DSP" (PeerDspChain unity/master-off/volume/parametric
   + ParametricToPeaking) and "v5 settings and shaping round-trip" (AppConfig defaults, NamedPeers,
   MainTabOrder, parametric PeerShaping, recording default = Both).
 * Logging (gated by the logging checkbox): master shaping switch, EQ-mode change, parametric band
   add/delete, peer rename/clear/delete, and the applied Appearance settings after Preferences close.
 * CLI: --list-profiles and --list-named-peers (read-only), in --help.
 * Version bumped to 5.0; About-box changelog, RELEASE_NOTES.md and README updated for v5.

Build clean; --selftest passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.Receiver/AudioReceiver.cs

@@ -206,7 +206,7 @@ public sealed class AudioReceiver : IDisposable
 
     /// <summary>Fired once per rendered block, right after <see cref="OnReceivedSamples"/> — the block
     /// boundary a single-file bypass recording uses to flush its per-peer sum.</summary>
-    public Action? OnRecordBlockComplete
+    public Action<int>? OnRecordBlockComplete
     {
         get => playoutEngine.OnRecordBlockComplete;
         set => playoutEngine.OnRecordBlockComplete = value;

src/RemSound.Receiver/PlayoutEngine.cs

@@ -170,8 +170,10 @@ internal sealed class PlayoutEngine : IWaveProvider
     }
 
     /// <summary>Fired once per rendered block, right after the mixed received tap — the block boundary a
-    /// single-file "bypass" recording uses to flush its per-peer sum.</summary>
-    public Action? OnRecordBlockComplete { get; set; }
+    /// split / "bypass" recording uses to flush its per-peer sum. The argument is the block's interleaved
+    /// float count (frames × channels), so the recorder can pad any peer that produced nothing this block
+    /// with silence and keep every track sample-locked to the render clock.</summary>
+    public Action<int>? OnRecordBlockComplete { get; set; }
 
     public WaveFormat WaveFormat { get; } = WaveFormat.CreateIeeeFloatWaveFormat(MixSampleRate, MixChannels);
 
@@ -822,7 +824,7 @@ internal sealed class PlayoutEngine : IWaveProvider
         // BothIndependent; without the tag both ended up in one recorder ring, doubling the
         // file's effective sample rate).
         DispatchReceivedSamples(mixBuf.AsMemory(0, outFloats), route);
-        OnRecordBlockComplete?.Invoke();
+        OnRecordBlockComplete?.Invoke(outFloats);
 
         Buffer.BlockCopy(mixBuf, 0, buffer, offset, outFloats * sizeof(float));
         return count;
@@ -899,7 +901,7 @@ internal sealed class PlayoutEngine : IWaveProvider
         // wasapi-slot ring (canonical single-lane slot in classic modes), so this fires
         // exactly once per real-time second.
         DispatchReceivedSamples(mixBuf.AsMemory(0, outFloats), RenderRoute.Mixed);
-        OnRecordBlockComplete?.Invoke();
+        OnRecordBlockComplete?.Invoke(outFloats);
 
         Buffer.BlockCopy(mixBuf, 0, buffer, offset, outFloats * sizeof(float));
         return count;