Bump to v3.0.0: Opus live latency, codec rename, profile-resume after update, save-through-lock

* New "Opus, live latency" codec mode: 2.5 ms frames (120 samples/ch at 48 kHz)
  via the float-input encode path. End-to-end codec delay drops to ~5 ms (vs
  ~12.5 ms at standard 10 ms Opus). Test on LAN: 400 pps/lane, zero missed /
  reordered / duplicate packets, ~15 ms one-way saved end-to-end.

* Wire-format change: AudioFormatInfo.FrameDurationMilliseconds renamed to
  FrameSamplesPerChannel (int sample-count at announced sample rate). Removes
  the lossy 48000*ms/1000 conversion that couldn't represent 2.5 ms. v3 <-> v3
  exact; v3 <-> v2 still passes audio (Opus decoder is self-describing from
  packet TOC) but v2 side over-sizes its buffer wildly. v2.x profiles auto-
  migrate via <120 sentinel rule in RemSoundSettingsStore (anything below 120
  is treated as legacy ms and multiplied by 48). Profile JSON key kept as
  OpusFrameMilliseconds via [JsonPropertyName] so old profile files still load.

* Codec dropdown rebuilt with use-case names: "PCM 48K 24 bit - uncompressed",
  "Opus, broadcast quality - loss tolerant", "Opus, live latency - for jamming
  and monitoring". Middle 10 ms option retired; saved 480-sample profiles
  collapse to broadcast quality (safer-side default).

* Profile auto-resume after self-update: RemSoundUpdater writes a one-shot
  _resume-after-update.txt sentinel containing the active profile title before
  exit; Program.Main reads + deletes it on next start and silently loads that
  profile, skipping the picker. Helper batch's robocopy /XF excludes the
  sentinel and the failure-branch cleans it up if the install aborts. Falls
  through to normal startup behaviour (StartWithProfileTitle or picker) if the
  sentinel is missing, empty, or names a profile that no longer exists.

* Read-only profile saves now go through on explicit Ctrl+S / File -> Save
  with a one-time TaskDialog warning ("Save anyway" / "Cancel" + Do-not-show-
  again). Lock continues to suppress the automatic unsaved-changes prompt on
  close / profile switch (its main job). AppConfig.SaveOnReadOnlyMessageSuppressed
  renamed to SaveOnReadOnlyWarningSuppressed; v2.x suppression flag is silently
  discarded since the behaviour changed and the user needs to see the warning
  once on each machine.

* Manual (readme.html) updated: codec table rewritten with the three new
  choices and corrected bandwidth figures, send-rate description updated, new
  sections "The same profile picks up automatically after an update" and
  "Saving on purpose while a profile is locked".

* Subsumes the never-separately-released v2.2 work: native Opus encoder
  (~97% less per-second memory churn on Opus send path via Concentus.Native),
  efficiency tidy-ups (item 4 ASIO probe rate, item 6 WaitHandle, item 7
  snapshot cache, items 14/16 heartbeat + discovery), legacy cleanup
  (items 30/34/35/36: KeepAlive infrastructure, drift drop/repeat/accumulator
  fields, fan-out cache stat). New diagnostic columns cpu/memMB/wsMB/
  allocKBps/captureMs/sendMs/recvMs/renderMs gated on Enable-logs.

About dialog updated with v3.0 block at top; v2.2 block retained for the
subsumed work.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/RemSound.Receiver/AudioReceiver.cs

@@ -274,7 +274,9 @@ public sealed class AudioReceiver : IDisposable
     /// <summary>
     /// Frame duration of the most-recently-active stream (10 ms PCM, 20 ms Opus). null when no
     /// stream is active. With multiple senders this picks the largest frame duration as the
-    /// codec floor — most conservative for the auto-tune.
+    /// codec floor — most conservative for the auto-tune. Returns ms (rounded up to the next
+    /// integer if the underlying sample-count yields a fractional duration, e.g. 2.5 ms → 3),
+    /// so the auto-tune always overestimates rather than underestimates the codec floor.
     /// </summary>
     public int? ActiveStreamFrameMs
     {
@@ -283,12 +285,20 @@ public sealed class AudioReceiver : IDisposable
             lock (sessionsLock)
             {
                 if (sessions.Count == 0) return null;
-                var maxFrame = 0;
+                var maxSamples = 0;
+                var sampleRate = 48000;
                 foreach (var s in sessions.Values)
                 {
-                    if (s.Format.FrameDurationMilliseconds > maxFrame) maxFrame = s.Format.FrameDurationMilliseconds;
+                    if (s.Format.FrameSamplesPerChannel > maxSamples)
+                    {
+                        maxSamples = s.Format.FrameSamplesPerChannel;
+                        sampleRate = s.Format.SampleRate > 0 ? s.Format.SampleRate : 48000;
+                    }
                 }
-                return maxFrame;
+                // Round up so a 2.5 ms frame reports as 3 ms — the auto-tune treats this as
+                // a floor, and overestimating by half a millisecond is safer than rounding
+                // down to 2 ms and pushing the buffer below the real codec frame size.
+                return (maxSamples * 1000 + sampleRate - 1) / sampleRate;
             }
         }
     }