feat(audit): Batch 20 — Windows/main-process (UI23, W12, W15, L131)

UI23: cookie sign-in + PO-token windows open with the app's resolved
theme background (passed from the IPC layer), no more white flash.
W12: multi-resolution fallback tray icon (16/24/32/48 via
addRepresentation dataURL, embedded in trayFallbackIcons.ts); decode +
scale factors verified in an Electron probe.
W15: hardwareAcceleration setting (default false = software rendering);
index.ts gates disableHardwareAcceleration on it after the portable
redirect; Appearance card switch with restart note; boot path verified.
L131: resolved by-design — clearing the queue acknowledges failures;
flashFrame (W10) covers attention, Diagnostics persists the record.

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

src/main/tray.ts

@@ -6,16 +6,7 @@
  */
 import { app, Tray, Menu, nativeImage, type BrowserWindow } from 'electron'
 import { getAppIconPath } from './binaries'
-
-// Fallback tray glyph (32×32 teal disc + white download arrow) used when no
-// build/icon.ico is present. Without this the tray is skipped (an empty image
-// makes an invisible/unclickable Windows tray entry), which would strand a
-// minimized-to-tray window with no way back. Embedded as base64 so it needs no
-// asset-bundling step.
-const FALLBACK_TRAY_PNG =
-  'iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAl0lEQVR4nO3TQQ6AIAxEUU7giV17bd0i' +
-  'aaDTmdqY0ISl/peirf11jvO6+/N5cHXKwlIIG6cQqngIoY5DiKy4C4G8aBwJohSArpIBmIgNKAWgDys' +
-  'AL8QGlANmCHZc8dUW1HEYEEFA6/d+B6q4CVAhwnHkb2DiUwCDkMRRBHpccQsRnXB8RLCAULxHMAAqbm0j5b4VoPRg1jzWxpzrS/JA7QAAAABJRU5ErkJggg=='
+import { FALLBACK_TRAY_PNGS } from './trayFallbackIcons'
 
 let tray: Tray | null = null
 // True once the user has chosen to really quit (tray menu, or app.quit from the
@@ -41,11 +32,19 @@ function show(getWindow: () => BrowserWindow | null): void {
 /** Create the tray icon + menu once. No-op if it already exists or the icon is missing. */
 export function createTray(getWindow: () => BrowserWindow | null): void {
   if (tray) return
-  // Prefer the real app icon; fall back to the embedded glyph when no icon.ico
-  // ships, so minimize-to-tray always has a tray to restore from.
+  // Prefer the real app icon; fall back to the embedded multi-resolution glyph
+  // when no icon.ico ships, so minimize-to-tray always has a tray to restore
+  // from — and stays crisp at 150%/200% DPI (W12). Without any icon the tray is
+  // skipped (an empty image makes an invisible/unclickable Windows tray entry),
+  // which would strand a minimized-to-tray window with no way back.
   let icon = nativeImage.createFromPath(getAppIconPath())
-  if (icon.isEmpty())
-    icon = nativeImage.createFromDataURL(`data:image/png;base64,${FALLBACK_TRAY_PNG}`)
+  if (icon.isEmpty()) {
+    icon = nativeImage.createEmpty()
+    for (const [scaleFactor, b64] of FALLBACK_TRAY_PNGS) {
+      // dataURL (not `buffer`) so the PNG is decoded — `buffer` is raw bitmap data.
+      icon.addRepresentation({ scaleFactor, dataURL: `data:image/png;base64,${b64}` })
+    }
+  }
   if (icon.isEmpty()) return
 
   tray = new Tray(icon)