Phase 3 (WA2c): move web Span into the adapter; SetSampleRate self-persists

Now that global-settings persistence is controller-owned, fold the persist into
SetSampleRate (sample rate is global; self-gated on FDevConnected). OnSampleRateSelect
becomes a thin wrapper. Web Span moves to TWebAdapter.OnSpan (keeps the valid-span
whitelist), so the last span coupling to MainForm is gone.

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

WebAdapter.pas

@@ -46,6 +46,7 @@ type
     procedure SyncAGCTop;
     procedure SyncVolume;
     procedure SyncDrive;
+    procedure SyncSpan;
     procedure SyncWfAGC;
     procedure SyncWfNF;
     procedure SyncMute;
@@ -72,6 +73,7 @@ type
     procedure OnAGCTop(DB: Integer);
     procedure OnVolume(V: Integer);
     procedure OnDrive(V: Integer);
+    procedure OnSpan(Hz: Integer);
     procedure OnWfAGC(On_: Boolean);
     procedure OnWfNF(On_: Boolean);
     procedure OnMute(On_: Boolean);
@@ -158,6 +160,24 @@ begin FSyncInt := V; FController.Invoke(@SyncDrive); end;
 procedure TWebAdapter.SyncDrive;
 begin FController.SetDrive(FSyncInt); end;   // rfDrive снимет память канала (ChannelController)
 
+procedure TWebAdapter.OnSpan(Hz: Integer);
+begin FSyncInt := Hz; FController.Invoke(@SyncSpan); end;
+
+procedure TWebAdapter.SyncSpan;
+// span ≡ sample rate. Принимаем только валидные значения (как десктоп-оверлей);
+// SetSampleRate сам пересоздаёт WDSP-канал + персистит (idempotent при том же rate).
+const
+  ValidSpans: array[0..5] of Integer = (48000, 96000, 192000, 384000, 768000, 1536000);
+var i: Integer;
+begin
+  for i := 0 to High(ValidSpans) do
+    if ValidSpans[i] = FSyncInt then
+    begin
+      FController.SetSampleRate(FSyncInt);
+      Exit;
+    end;
+end;
+
 procedure TWebAdapter.OnWfAGC(On_: Boolean);
 begin FSyncBool := On_; FController.Invoke(@SyncWfAGC); end;