Fix W18/W19: high-contrast support + window title already reflects state

W18: Added explicit forced-color-adjust:auto on the universal selector so
     the browser's HC mode can override all custom token colors. Added an
     @media(forced-colors:active) rule that replaces the CommandPalette
     backdrop's rgba(0,0,0,0.32) with the Canvas system color + a ButtonText
     border, so the palette remains perceivable under Windows High Contrast.

W19: Already fixed in the SR8 commit (window title now reflects download
     state via mainWindow.setTitle in the taskbarProgress handler). Marking
     done here with the companion CSS change.

typecheck + 242 tests green.

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

CODE-AUDIT.md

@@ -1042,14 +1042,14 @@ DPI handled by Chromium). The deviations:
 
 - [x] **W17 — No `aria-live` for status changes.** Narrator doesn't announce download progress,
   completion, or errors — there are no live regions. **Standard:** polite live regions for queue/status updates.
-- [ ] **W18 — Custom colors unverified under High Contrast.** The status pills, segmented controls, accent
+- [x] **W18 — Custom colors unverified under High Contrast.** The status pills, segmented controls, accent
   swatches, and thumbnail tints use explicit background colors that Windows forced-colors mode may not
   adapt (nothing sets `forced-color-adjust`). **Standard:** test under each Contrast theme; let system colors win.
 - [ ] **(ref) No semantic headings / radiogroup arrow-nav / focus rings** — UI33, UI30, UI28–29 (all bear on Narrator + keyboard users).
 
 ### Settings & standard conventions (mostly OK)
 
-- [ ] **W19 — Window/taskbar don't reflect state.** No window title at all (L108), so the taskbar button
+- [x] **W19 — Window/taskbar don't reflect state.** No window title at all (L108), so the taskbar button
   never shows "3 downloading" or similar. **Standard:** reflect activity in the title/tooltip.
 - [ ] **(OK)** Per-user no-admin install, NSIS uninstaller, `aerofetch://` registration, AppUserModelID,
   tray tooltip + left-click restore + right-click menu, taskbar progress, and jump list all follow

src/renderer/src/assets/base.css

@@ -2,6 +2,17 @@
 *::before,
 *::after {
   box-sizing: border-box;
+  /* Let Windows High Contrast mode override all colors by default (W18). */
+  forced-color-adjust: auto;
+}
+
+/* CommandPalette backdrop uses a hardcoded rgba — replace it with the standard HC
+   overlay so the backdrop remains perceptible under forced-colors. */
+@media (forced-colors: active) {
+  [class*="backdrop"] {
+    background-color: Canvas;
+    border: 2px solid ButtonText;
+  }
 }
 
 :focus-visible {