Phase 3 (batch 10): route sample-rate/span change through controller

Span ≡ sample rate in this app; OnSampleRateSelect (overlay dropdown) is a
fairly self-contained heavy-class item.

- TRadioController.SetSampleRate(Hz): sets FSampleRate/FSpanHz + band cache,
  recreates the WDSP channel (ChangeSampleRate = Close+FlushQueue+Open),
  pushes the new DDC rate to the radio, and restores full DSP state
  (mode/volume/filter/NR/NB/SNB/ANF/AGC-top/AGC/shift).
- Fixes the same latent AGC cast bug as earlier batches: the inline restore
  used SetAGC(TWDSPAGCMode(FAGCMode)) (index cast); now goes through the
  shared ApplyAGCToEngine mapping.

MainForm: OnSampleRateSelect is a thin wrapper (global-settings SaveGlobal
stays in UI). OnControllerState(rfSampleRate) renders the rate overlay and
recomputes AGC display lines (UpdateAGCLines needs UI spectrum width).
Dropped the cosmetic ProcessMessages pre-paint. Startup paths that set
FSampleRate directly + RecreateDSPEngine left as-is. Builds clean, links.

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

RadioController.pas

@@ -589,7 +589,48 @@ procedure TRadioController.SetSpan(Hz: Integer);
 begin FSpanHz := Hz; Changed(rfSpan); { TODO wiring } end;
 
 procedure TRadioController.SetSampleRate(Hz: Integer);
-begin FSampleRate := Hz; Changed(rfSampleRate); { TODO wiring: RecreateDSPEngine } end;
+// Смена частоты дискретизации DDC. В этом приложении span ≡ sample rate.
+// Несёт: пересоздание WDSP-канала (Close+FlushQueue+Open), новый rate в
+// трансивер и полное восстановление DSP-состояния. Сохранение в global
+// settings + рендер overlay/AGC-линий остаются в UI (OnControllerState).
+begin
+  if (Hz <= 0) or (Hz = FSampleRate) then Exit;
+  FSampleRate := Hz;
+  FSpanHz     := Hz;
+  FBandCache[FCurrentBand].SpanHz := FSpanHz;   // для обратной совместимости
+
+  // 1. Останавливаем WDSP и меняем rate (Close + FlushQueue + Open).
+  if FWDSPReady and Assigned(FDSPEngine) then
+  begin
+    FWDSPReady := False;
+    FDSPEngine.ChangeSampleRate(Hz);
+  end;
+
+  // 2. Новый rate трансиверу (после остановки DSP — пакеты сразу с верным rate).
+  if Assigned(FNetwork) and FNetwork.Connected then
+    FNetwork.ConfigureDDCs(1, Hz div 1000, 0, FDitherEnabled, FRandomEnabled);
+
+  // 3. Восстанавливаем DSP-состояние (ChangeSampleRate пересоздал канал).
+  if Assigned(FDSPEngine) then
+  begin
+    FWDSPReady := FDSPEngine.Initialized;
+    if FWDSPReady then
+    begin
+      FDSPEngine.SetMode(FMode);
+      FDSPEngine.SetVolume(FVolume / 100.0);
+      ApplyModeFilter;
+      FDSPEngine.SetNRMode(FNRMode);
+      FDSPEngine.SetNBMode(FNBMode);
+      FDSPEngine.SetSNB(FSNB);
+      FDSPEngine.SetANF(FANF);
+      FDSPEngine.SetAGCTop(FAGCTop);
+      ApplyAGCToEngine;   // единый маппинг (раньше здесь был ошибочный каст индекса)
+      if Assigned(FNetwork) and FNetwork.Connected then
+        FDSPEngine.SetShift(FVfoA - FCenterFreq);
+    end;
+  end;
+  Changed(rfSampleRate);
+end;
 
 procedure TRadioController.SetCTun(On_: Boolean);
 begin