Add emulator/ENV-VARS.md -- pod (L4*/DPLARG) + host emulator env var catalog

Documents L4VIDEO/VIDEOFORMAT/L4GAUGE/L4PLASMA/L4TIMER/L4SOUND/L4CONTROLS/L4DPLCFG/L4EYES/DPLARG (values, meanings, which are getenv-read vs batch-only, the L4VIDEO two-script gotcha) + the VPX_/VWE_/VDB_/VRVIEW_ host vars.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

emulator/ENV-VARS.md

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+# Environment variables — Tesla pod (game) + emulator (host)
+
+Two separate environments:
+1. **The DOS pod/game environment** — set inside DOSBox by `SETENV.BAT`
+   (dev/archive) or `VGL_LABS/PARAMETR.BAT` (production), consumed by
+   BTL4OPT/RPL4OPT and the MUNGA runtime.
+2. **The host emulator environment** — set on Windows before launching, read by
+   the DOSBox-X fork's HLE devices (see LAUNCH.md, VDB-NOTES.md).
+
+---
+
+## 1. DOS pod/game environment
+
+### SETENV.BAT positional args (how the vars get set)
+
+`call setenv.bat <1> <2> <3> <4> <5>` — our confs use e.g. `r f s p`:
+
+| Arg | Values | Sets |
+|-----|--------|------|
+| 1 | `t`=Thrustmaster, `r`=RIO | `L4CONTROLS` |
+| 2 | `s`=slow clock, `f`=fast clock | `L4TIMER` |
+| 3 | `s`=sound, `n`=nosound | `L4SOUND` + AWE mixer init |
+| 4 | `p`=plasma+gauges, `g`=gauges, `n`=none, `r`=review | `L4GAUGE` + `L4PLASMA` |
+| 5 | `i`=intercom, `n`=none | `L4INTERCOM` |
+
+No args = RIO, SLOW, SOUND, none, no-intercom.
+
+### The variables
+
+**Read by the game (`getenv`, confirmed in CODE/):**
+
+| Var | Values | Meaning |
+|-----|--------|---------|
+| **L4CONTROLS** | `RIO,KEYBOARD` / `THRUSTMASTER,KEYBOARD` | Control input source(s). RIO = the real cockpit board (our vRIO); Thrustmaster = PC gameport joystick. |
+| **L4GAUGE** | `640x480x16` / `640x480x8` / *(empty)* | Cockpit gauge (VDB) render mode. Keys into `GAUGE\L4GAUGE.INI` for mode/width/height/**bytesPerLine**/sizeInKB/**granularityInKB**/pageFcnPtr/special. Empty = no gauge renderer created. (16 = pod/plasma; 8 = review/camera.) See VDB-NOTES.md — RP's INI granularity was the gauge-decode bug. |
+| **L4PLASMA** | `com2` / `com1` / *(empty)* | Plasma score/status panel serial port. Empty = no plasma. Our pods use COM2. See [[plasma-display-readout]]. |
+| **L4INTERCOM** | `ON` / *(empty)* | Cockpit intercom (PTT/relay via the AWE mixer + L4ICOM). Empty = off. |
+| **L4DPLCFG** | `rpdpl.ini` / `btdpl.ini` | Per-arena DPL config (fog/light/objectpath per map+time+weather). Defaults from the game dir's SETENV. |
+| **L4EYES** | `"x y z rx ry rz [r]"` (6 floats + optional type) | Division 3D camera EYE offset/rotation. Present = "disconnected eye" (outside/relative view); trailing `r` = offset relative to the vehicle. Usually UNSET (first-person). |
+| **DPLARG** | arg string (see below) | The Division 3D renderer's full argument string. MUST be set for the Division card to come up (else `Verify(DPL_Arg)` exits). |
+
+**Batch-only controls (NOT read by the game via getenv — they shape the above):**
+
+| Var | Values | Meaning |
+|-----|--------|---------|
+| **L4VIDEO** | `svga` / `ntsc` / `OFF` | Division 3D output format, OR an on/off switch — **depends on the script** (see note). NOT read by game code. |
+| **VIDEOFORMAT** | `svga` / `ntsc` | (SETENV path) the `/video~` format fed into DPLARG. Defaults `svga`. |
+| **L4TIMER** | `FAST` / *(empty=SLOW)* | HMI SOS real-time interrupt clock: FAST≈28Hz vs unset≈18.2Hz BIOS. Our conf default = FAST (per-fleet CPU choice historically). See [[l4timer-fast-default]]. |
+| **L4SOUND** | `OFF` / `ON` / `CAMERA` / *(empty)* | Gates the AWE32 mixer/upload init in SETENV. The EXE does NOT read it (red herring for in-game audio); sound presence is really the AWE hardware being initialized. |
+
+### L4VIDEO — the two-script gotcha
+
+- **Production `PARAMETR.BAT`**: `L4VIDEO` IS the format — `%5`=SVGA→`L4VIDEO=svga`,
+  NTSC→`L4VIDEO=ntsc`, then `DPLARG .../video~%L4VIDEO%~...`. A `:VIDEOOFF` path
+  skips DPLARG (no 3D); `L4VIDEO` is never literally "OFF" there.
+- **Archive `REL410/{RP,BT}/SETENV.BAT`** (our confs): `L4VIDEO` is an ON/OFF
+  switch — `if "%L4VIDEO%"=="OFF" goto VIDEODONE` skips DPLARG; the format comes
+  from **`VIDEOFORMAT`** instead.
+
+So on OUR path: leave `L4VIDEO` unset for normal 3D, `L4VIDEO=OFF` to suppress
+the Division card (non-rendering host roles only), and pick the format with
+`VIDEOFORMAT=svga|ntsc`.
+
+### DPLARG sub-fields
+
+`/tranny~.\vrendmon.btl~ /i860~.\vrnostex.mng~ /device~0x150~ /video~<fmt>~ /pipes~1~ /qual~0x14~ /system_tex~0~`
+
+| Field | Meaning |
+|-------|---------|
+| `/device~0x150~` | VPX/VelociRender board I/O port (our HLE lives here). |
+| `/video~svga\|ntsc~` | Division output format (from L4VIDEO or VIDEOFORMAT). |
+| `/qual~0x14~` | Render quality flags. |
+| `/pipes~1~` | Render pipe count. |
+| `/tranny~vrendmon.btl~` | Transform/monitor config blob. |
+| `/i860~vrnostex.mng~` | i860 microcode / no-system-texture image. |
+| `/system_tex~0~` | System-texture toggle. |
+
+### Related DOS vars (not L4*)
+
+`HEAPSIZE` (game heap, e.g. 15000000), `BLASTER`/`AWE_FRONT`/`AWE_REAR` (SB16/
+dual-AWE32 config), `TEMP=c:\`, `VIDEOFORMAT` (above). Production-only:
+`PREFGAME` (RP/BT), `PODTYPE`/PODSET, `PREFMODE`/`PREFOPT`/`PREFSWITCH`,
+`PRELOAD`, `REVIEW`/`CAMERA` (host role), `SPOOLSIZE`, `NETRESOURCE`/`NDSID`/
+`NETCLIENT` (Netware, unused under emulation).
+
+---
+
+## 2. Host emulator environment (set on Windows before launch)
+
+Set by `render-bridge\launch_pod.ps1` / its flags; see LAUNCH.md.
+
+- **VPX board HLE**: `VPXLOG` (wire log path), `VPX_RESPOND=1`, `VPX_RENDER=1`,
+  `VPX_EXPLODE=1` (pentapus 7-display), `VPX_DUMPDIR`, `VPX_FIFODUMP`,
+  `VPX_FIFOSOCK=8621` (bridge tee), `VPX_NOMAIN=1`, `VPX_CLEAR`,
+  `VPX_WIN<g>`/`VPX_MAIN` (window geometry), `VPX_NO_PICK=1` (disable reticle
+  raycast).
+- **Sound (dual AWE32/EMU8000)**: `VWE_AWE32=1`, `VWE_AWE_ROM=<1MB GM rom>`,
+  `VWE_AWE_LOG=1`, `VWE_AWE_WAV=<prefix>`.
+- **RIO tap**: `RIO_TAP=<path>` (logs COM1 TX/RX with host-us timestamps).
+- **VDB display diagnostics** (default-off, see VDB-NOTES.md): `VDB_SCAN`,
+  `VDB_PALDUMP=<prefix>`, `VDB_BASE=<hex>`, `VDB_REALSTRIDE`, `VDB_APPLYMASK`.
+- **GL bridge**: `VRVIEW_MIPMAP` (-Mipmap flag), `VRVIEW_FILTER=linear`,
+  `VRVIEW_HUDSCALE`, `FP_UPOFF`/`FP_FWDOFF` (seat trim), `BRIDGE_FPS`.
+
+Net map: pod 200.0.0.113, .NET console/host 200.0.0.1, Mac console 200.0.0.10,
+netnub TCP 1501. Related: LAUNCH.md, VDB-NOTES.md, NET-NOTES.md.