v5.2: stability and polish — deep-audit bug fixes + install-flow fixes

Verified findings from a multi-dimension code audit, plus the two install-flow bugs:
- Fix Opus encoder use-after-free on a codec/rate change while streaming (guard swap vs encode).
- Fix "both" single-file recording dropping audio + drifting (drain both directions in lockstep).
- Fix broken clip counter, UPnP teardown on exit, auto-update-restart foreground grant, and a
  malformed-Opus-format packet orphaning a playout session forever.
- Post-install relaunch now respects start-minimised; uninstall is path-aware so it won't clear a
  different copy's run-at-startup.
- Perf/hygiene: cache AppConfig off UI hot paths, fold per-peer EQ+gain into one pass, deterministic
  disposal (tray menu, timers, COM shortcut, Process handles, process meter), ring-buffer overflow
  guard, receiver session-lock fix, remote-control allow-list moved onto the UI thread.
- Remove dead code (two IsAsioBackend, SessionPlayout.Reset, IsSameEndpoint, RemSoundUpdater
  IDisposable); several stale-doc fixes.

Deferred (not in this release): drift-estimator tweak, peer-discovery pruning, uninstall retry-loop,
encryption nonce. Wire format unchanged (interops v3.3-v5.1). Version -> 5.2.

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

src/RemSound.App/CueSounds.cs

@@ -51,7 +51,13 @@ internal static class CueSounds
             }
         }
         catch { return Array.Empty<string>(); }
-        return matches.OrderBy(m => m.Order).Select(m => m.Name).ToList();
+        var ordered = matches.OrderBy(m => m.Order).ToList();
+        // If numbered variants exist, drop the bare unnumbered file: it labels as "Sound 1" (below), the
+        // same as "<cue> 1.wav", so the two would show as indistinguishable "Sound 1" rows a screen-reader
+        // user can't tell apart. The bare name is a legacy single-file fallback; numbered is what ships.
+        if (ordered.Exists(m => m.Order >= 1) && ordered.Exists(m => m.Order == 0))
+            ordered.RemoveAll(m => m.Order == 0);
+        return ordered.Select(m => m.Name).ToList();
     }
 
     /// <summary>The "Sound N" label for a variant filename, for the Preferences listbox.