test(render): fail the offline pixel gate on stray camera input

The offline capture window is minimised but still focusable, so a scroll or key press from whoever is at the keyboard can move the camera mid-capture. That yields two screenshots of the same scene from different camera positions and an enormous, entirely spurious pixel difference - which happened during slice V4b and was correctly discarded rather than interpreted. The gate now detects camera-affecting input in the client log and exits 2, so a perturbed run cannot be mistaken for a rendering regression in either direction.

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

tools/run-offline-pixel-gate.ps1

@@ -161,6 +161,22 @@ finally {
 $captures = Get-ChildItem (Join-Path $Out 'screenshots') -Filter *.png
 Write-Step "captured $($captures.Count) screenshot(s) into $Out"
 
+# The offline window is minimised but still focusable, so a stray scroll or key
+# press from whoever is at the keyboard can move the camera mid-capture. That
+# produces two screenshots of the same scene from different camera positions —
+# a huge, entirely spurious pixel difference. This actually happened during
+# slice V4b. Detect it and fail loudly rather than let a comparison be
+# interpreted as a rendering regression.
+$cameraInput = Select-String -Path $log -Pattern 'ScrollUp|ScrollDown|ZoomIn|ZoomOut|CameraZoom' `
+    -CaseSensitive -ErrorAction SilentlyContinue
+if ($cameraInput) {
+    Write-Host ''
+    Write-Host '[pixel-gate] ABORTED: camera-affecting input reached the capture window.' -ForegroundColor Red
+    Write-Host '            The capture is not comparable. Re-run without touching the machine.' -ForegroundColor Red
+    $cameraInput | Select-Object -First 5 | ForEach-Object { Write-Host "  $($_.Line)" -ForegroundColor Red }
+    exit 2
+}
+
 # --- 4. Compare against the baseline -----------------------------------------
 if (-not $Baseline) {
     Write-Step 'no baseline supplied; capture only'