feat: QO-100 beacon AO-40 FEC decode end-to-end (Milestone 2)

Full chain now decodes the QO-100 central beacon to 256-byte AO-40 frames
on-air (frames>0, RS errors=0). Builds on M1 (stable BPSK demod).

FEC backend (BeaconFEC.pas, TBeaconFEC):
- AO-40 FEC: distributed sync (65 bit, step 80) -> 80x65 deinterleave ->
  Viterbi r=1/2 k=7 -> CCSDS descramble -> 2x RS(160,128). Links system
  libfec (Karn) load-time (libfec.so/.dll/.dylib). Viterbi AO-40 [0x4F,-0x6D]
  remapped to libfec [0x6D,0x4F]. Validated against gr-satellites reference
  vectors (fectest2: exact 256-byte frame, 0 mismatches).

DBPSK Manchester frontend (BeaconDecoder.pas):
- Chip-rate (800) processing: RRC matched filter -> ML signal-times-slope
  timing recovery -> Costas -> Manchester combine (block phase select) ->
  differential decode -> soft symbols to FEC.
- Carrier acquisition: squaring-FFT estimates the residual (carrier at +-pi/chip
  defeats decision-directed Costas), one-shot pulls it to DC via residual NCO.
- Costas frequency offload into pre-RRC NCO (with deadband) tracks LNB drift
  without hitting the +-pi Costas clamp.
- ML TED replaces Gardner, which degenerates on the Manchester chip stream.

Temporary on-air diagnostics retained (IQ dump + STATE log) pending wider
signal validation; to be removed before final cleanup.

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

BeaconScopeForm.pas

@@ -44,7 +44,7 @@ begin
   Caption := 'QO-100 Beacon — Constellation';
   BorderStyle := bsSizeable;
   Width := 360;
-  Height := 510;
+  Height := 560;
   Position := poScreenCenter;
 
   FBox := TPaintBox.Create(Self);
@@ -160,6 +160,12 @@ begin
     C.TextOut(14, py + 90, 'INVERT   ' + IfThen(FCtl.BeaconDecodeInvert, 'ON', 'OFF'));
   C.TextOut(14, py + 108, Format('RATE     Fs %.0f  Fdec %.0f  sps %.1f',
                                  [S.FsHz, S.FdecHz, S.Sps]));
+
+  // ----- FEC (AO-40) -----
+  if S.HasFrame then C.Font.Color := FTheme.MeterOn else C.Font.Color := FTheme.TextDim;
+  C.TextOut(14, py + 132, Format('FRAMES   %d   (RS err %d)', [S.Frames, S.LastRSErr]));
+  C.Font.Color := FTheme.TextDim;
+  C.TextOut(14, py + 150, Format('MANCHESTER  phase %d', [S.ManPhase]));
 end;
 
 end.