Bridge: VRVIEW_MIPMAP option + launch_pod -Mipmap flag (RP checkerboard shimmer)

RP's high-frequency checkerboard track floor aliases/moires without mipmaps
(reads as "flashing geometry" in motion; user's texture-interpolation call).
vrview_gl _tex() now builds mipmaps + trilinear/anisotropic filtering under
VRVIEW_MIPMAP=1 (keeps point-sample look up close; off by default = authentic
i860, BT-identical). launch_pod.ps1 gains -Mipmap so it's set at BOOT -- never
restart the bridge mid-mission (GL-context churn starves the RIO ACK deadline).

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

emulator/render-bridge/launch_pod.ps1

@@ -16,8 +16,13 @@ param(
     [string]$BridgePos = '2020,20',   # Division head slot (explode layout)
     [switch]$NoBridge,
     [switch]$NoSound,
-    [switch]$ShowNative               # also show the native Division window
+    [switch]$ShowNative,              # also show the native Division window
                                       # (wire-decode diagnostic; black clear)
+    [switch]$Mipmap                   # VRVIEW_MIPMAP=1: mip-filter minified
+                                      # textures (kills RP's checkerboard-floor
+                                      # shimmer). Non-authentic (board had no
+                                      # mipmaps); set at BOOT so no mid-mission
+                                      # bridge restart churns the RIO.
 )
 $ErrorActionPreference = 'Stop'
 New-Item -ItemType Directory -Force $Work | Out-Null
@@ -77,6 +82,8 @@ if (-not $NoBridge) {
     # park the bridge window on the Division head slot (SDL honors this at
     # window creation)
     $env:SDL_VIDEO_WINDOW_POS = $BridgePos
+    if ($Mipmap) { $env:VRVIEW_MIPMAP = '1' }
+    else { Remove-Item Env:VRVIEW_MIPMAP -ErrorAction SilentlyContinue }
     # bridge rides the socket tee (retries until the device listens); the
     # fifodump path is its catch-up source if it ever (re)starts mid-mission.
     # Launch with pyw (windowless pythonw), NOT py: py opens a console window