emulator: in-fork virtual RIO cockpit board (serial1=rio)

Emulate the cockpit RIO board natively inside the DOSBox-X fork, driven by
an SDL game controller + host keyboard -- no external vRIO process and no
named pipe. The game<->board round trip runs in-process at the emulated
UART's own cadence, so the serial round-trip dropouts (livelock, TXMAXIDLE,
rxburst, 15s retry) can't occur.

- serialrio.{cpp,h}: RIO 9600-8N1 device state machine + protocol codec +
  input mapping, transcribed from the vRIO app (VRioDevice + Protocol +
  InputRouter/BindingProfileFormat), minus transport/pacer/UI/locks.
  B0 = gamepad (5 axes + joystick column). B1 = keyboard field: MFD banks on
  the letter rows, F-keys = Secondary/Screen, numpad = flight controls,
  LShift/LCtrl throttle slew; PAUSE/ScrollLock toggle panel<->DOS; vRIO-
  grammar bindings file via bindings:/VWE_RIO_BINDINGS.
- vpx-device/README.md: device notes + apply steps (the DOSBox-X src tree is
  git-ignored, so this dir is the tracked source of truth; the three sdlmain
  keyboard-hook edits are documented there).
- net_{loop,rp}_rio.conf + deploy templates; render-bridge/
  gauge_arena_rio_sound.conf (standalone -egg trim); pod-launch --rio
  (mutually exclusive with --pipe).

Additive: real pods keep directserial realport:COM1; vRIO-over-pipe keeps
namedpipe pipe:vrio. Validated live 2026-07-22 (pad + keyboard field +
console networking) on the dist install.

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

emulator/render-bridge/gauge_arena_rio_sound.conf

@@ -0,0 +1,80 @@
+# IN-FORK RIO variant of gauge_arena_pipe_sound.conf: bare -egg arena1 run
+# (no netnub/console) with the RIO board emulated NATIVELY inside DOSBox-X
+# (serial1=rio) -- SDL game controller + host keyboard field (PAUSE toggles
+# panel/DOS). No vRIO process, no pipe. Everything else identical to the
+# pipe trim (see its comments for the rationale of each section).
+[sdl]
+output=opengl
+# higher,higher not highest: HIGH_PRIORITY_CLASS starved the host desktop;
+# with the retry patches a rare dropout self-recovers (see gauge_rio.conf).
+priority=higher,higher
+[dosbox]
+memsize=32
+machine=svga_s3
+[cpu]
+core=dynamic
+cputype=pentium
+cycles=max
+[sblaster]
+sbtype=sb16
+sbbase=220
+irq=5
+dma=1
+hdma=5
+[mixer]
+# match the EMU8000s' native rate (no resample) and buffer ~60ms so brief
+# emulation-thread stalls (RIO retry recovery) don't audibly chop
+rate=44100
+blocksize=1024
+prebuffer=60
+[ne2000]
+# bare -egg run WITH the packet stack resident (as production AUTOEXEC did);
+# slirp = user-mode NAT, no LAN peers -- fine for a solo run.
+ne2000=true
+nicbase=340
+nicirq=3
+backend=slirp
+[joystick]
+# the in-fork RIO owns the game controller (SDL); keep the DOS gameport +
+# mapper auto-binding off so nothing else grabs the pad.
+joysticktype=none
+[serial]
+# in-fork virtual RIO board on COM1 (pad:<n> / inverty / bindings:<path>
+# optional); plasma display stays on the vPLASMA pipe (optional).
+serial1=rio
+serial2=namedpipe pipe:vplasma
+[autoexec]
+mount c "C:\VWE\TeslaRel410\ALPHA_1"
+mount d "C:\VWE\TeslaRel410\emulator\net-boot"
+d:
+echo === loading NE2000 packet-driver stack (as production AUTOEXEC did) ===
+d:\lsl
+d:\ne2000
+d:\odipkt
+c:
+cd \REL410\BT
+set VIDEOFORMAT=svga
+rem production pod card init (PARAMETR.BAT:181-186): DIAGNOSE + AWEUTIL per
+rem card -- AWEUTIL /S does the EMU8000 bring-up and DRAM detect the HMI SOS
+rem driver relies on; skipping it left the cards uninitialized (silent).
+rem aweutil /s SKIPPED for now: it verifies the AWE32 GM ROM, which the
+rem emulated cards lack (hangs in a retry loop) -- restore once the ROM is
+rem dumped from a real card. diagnose /s kept (passes, sets mixer config).
+set BLASTER=A220 I5 D1 H5 P330 T6
+c:\sb16\diagnose /s
+set BLASTER=A240 I7 D3 H6 P300 T6
+c:\sb16\diagnose /s
+set BLASTER=A220 I5 D1 H5 P330 T6
+set TEMP=c:\
+rem arena1 city mission (TESTARN.EGG: map=arena1, time=day), RIO attached,
+rem bare -egg launch (no netnub) = the real-world test-egg setup.
+set HEAPSIZE=15000000
+set L4GAUGE=640x480x16
+call setenv.bat r f s p
+32rtm.exe -x
+rem stdout -> log (this optimized build still emits DEBUG_STREAM lines).
+btl4opt.exe -egg testarn.egg > c:\weaponlog.txt
+32rtm.exe -u
+echo ALPHA1-RUN-DONE
+pause
+