style(install-windows): filter winget's spinner frames out of the log

Piping winget to Out-Host defeats its carriage-return redraw, so every spinner
and progress-bar frame lands as its own line. Filters the frames, keeps the
messages. Block characters spelled by code point to keep the file ASCII.

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

install-windows.ps1

@@ -43,8 +43,17 @@ function Update-SessionPath {
 function Install-Winget {
     param([string]$Id, [string]$Label)
     Write-Step "Installing $Label"
+    # winget animates a spinner ("-\|/") and a block progress bar using carriage
+    # returns to redraw one line in place. Piping it defeats that: PowerShell
+    # splits on the CRs, so every frame arrives as its own line and the log fills
+    # with dozens of lone dashes and bar snapshots. Drop the frames and keep the
+    # sentences. The block characters are spelled by code point because every
+    # .ps1 here must stay ASCII (tests/test_smoke.py enforces it).
+    $bar = "$([char]0x2588)$([char]0x2592)"
     winget install --id $Id -e --source winget `
-        --accept-package-agreements --accept-source-agreements --disable-interactivity | Out-Host
+        --accept-package-agreements --accept-source-agreements --disable-interactivity |
+        Where-Object { $_ -notmatch "[$bar]" -and $_ -notmatch '^\s*[-\\|/]\s*$' -and $_.Trim() } |
+        Out-Host
     # winget returns non-zero when the package is already installed / up to date;
     # that's not a failure for us. Verify presence after refreshing PATH instead.
     Update-SessionPath