Fix launch_live.ps1: don't enable Dave's native render thread

VPX_RENDER=1 was copied in from launch_pod.ps1's defaults without thinking it
through -- it starts vpxlog.cpp's OWN native GL render thread (rt_main),
which is redundant with (and contends against) our reconstructed renderer
riding the FIFOSOCK tee. Live-caught: with it set, wire delivery stalled at
command 8 for 90+s (window rendered, but slowly/poorly per live observation);
removing it, the same mission reached command 21,488 (10 frames) in the same
window. My two earlier successful ad-hoc bring-up tests had already removed
this env var by hand -- the script just hadn't caught up.

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

emulator/render-bridge/launch_live.ps1

@@ -32,12 +32,14 @@ Remove-Item "$Work\live.fifodump", "$Work\pod_out.txt", "$Work\pod_err.txt" -Err
 # --- the vpxlog C012 device env (host-side) ---
 $env:VPXLOG       = "$Work\vpxresp.txt"
 $env:VPX_RESPOND  = '1'                     # answer as the transputer would
-$env:VPX_RENDER   = '1'
 $env:VPX_NOMAIN   = '1'                     # no native Division window
 $env:VPX_CLEAR    = '0,0,0'
 $env:VPX_FIFODUMP = "$Work\live.fifodump"   # archival copy alongside the socket
 $env:VPX_FIFOSOCK = "$Port"                 # the live tee our renderer rides
-Remove-Item Env:VPX_EXPLODE -ErrorAction SilentlyContinue   # no pentapus
+# VPX_RENDER intentionally NOT set: that starts Dave's native GL render thread
+# (rt_main) inside dosbox-x itself -- redundant with (and contends against) our
+# own reconstructed renderer riding the FIFOSOCK tee.
+Remove-Item Env:VPX_RENDER, Env:VPX_EXPLODE -ErrorAction SilentlyContinue   # no native renderer, no pentapus
 if ($Sound) {
     $env:VWE_AWE32   = '1'
     $env:VWE_AWE_ROM = (Resolve-Path "$PSScriptRoot\..\roms\awe32.raw").Path