The wireframe stands against black

Alt+W held the sky dome solid so the edges had something to read
against. Looking at it, the dome was the problem: lit, fogged and
filling the upper half, it washed out everything behind the near
geometry. A whole structure over the track in the middle distance was
invisible until the sky came away.

So the view now clears to BLACK under wireframe and the sky pass is
skipped entirely. Skipping costs nothing - the dome only ever covers
pixels the clear already owns - and it removes the two fill-mode
brackets that used to wrap the pass, so the frame is simpler than it
was. Both changes are conditional on gWireframe; the solid path clears
to the fog colour and draws its sky exactly as before.

Fog still applies to the edges, which is why the middle distance tints
toward the fog colour instead of staying bright. That is depth
information, so it stays.

environ.ini's template and BUILD.md both said the sky stayed solid.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

RP_L4/RPL4ENVIRON.cpp

@@ -411,9 +411,9 @@ namespace
 "# ---- Developer / testing ----------------------------------------------------\n"
 "\n"
 "# Nonzero arms the debug keys. Two of them do something in this build:\n"
-"#   Alt+W   wireframe. The sky dome stays solid so the edges have\n"
-"#           something to read against, and the gunsight and cam-ship\n"
-"#           HUD stay solid too.\n"
+"#   Alt+W   wireframe. The sky is not drawn and the view clears to\n"
+"#           black, so the edges stand on their own; the gunsight and\n"
+"#           cam-ship HUD stay solid.\n"
 "#   Alt+E   write the event queue to the log.\n"
 "# The others are stubs the 2007 DPL->Direct3D port left behind and do\n"
 "# nothing at all. They are named here so a dead key is not mistaken for\n"