Deck chrome: neutral surfaces, borders and text (no navy leftovers)

- The study feed's progress header and bottom pager no longer use the old
  navy glass: new .study-chrome class uses the neutral surface token
  (same gray as the cards, #2f2f2f in dark), the neutral border
  (8% white in dark, #e5e5e5 in light) and a neutral shadow.
- Close tile, streak pill and XP pill now use --surface-sunken /
  --text-muted, matching the app's other buttons and chips; the close
  glyph is the shared XIcon.
- Bottom pager: counter in --text, arrows in --text-muted.
- .glass (mobile header) no longer has the hardcoded #101720 navy; it is
  now color-mix of the surface token. Removed the unused --color-night-*
  tokens and the last night- usage (create screen sticky bar).
- Hidden the 'Swipe up' hint on desktop, where it collided with the
  bottom pager.

New deck-chrome suite: 15/15 (computed surfaces/borders/text in both
themes, no navy); pwa 16/16, final-ux 12/12, security 8/8, contrast 20/20.

app/globals.css

@@ -35,12 +35,6 @@
   --color-aurora-lilac: #c3b6f0;
   --color-aurora-peach: #f6cdb4;
 
-  --color-night-50: #f6f9fc;
-  --color-night-700: #1d2733;
-  --color-night-800: #151d27;
-  --color-night-900: #101720;
-  --color-night-950: #0a1017;
-
   --font-sans: -apple-system, BlinkMacSystemFont, ui-sans-serif, system-ui,
     "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif,
     "Apple Color Emoji", "Segoe UI Emoji", "Noto Color Emoji";
@@ -302,11 +296,20 @@ body {
   /* Tailwind emits both the prefixed and standard properties; hand-written
      backdrop-filter gets minified down to -webkit- only, which paints nothing. */
   @apply backdrop-blur-xl backdrop-saturate-150;
-  background: color-mix(in oklab, white 68%, transparent);
+  background: color-mix(in oklab, var(--surface) 70%, transparent);
   border-bottom: 1px solid var(--hairline);
 }
-.dark .glass {
-  background: color-mix(in oklab, #101720 70%, transparent);
+
+/* Study-feed chrome (progress header + bottom pager): the same neutral
+   surface as the cards, with a neutral border and shadow. */
+.study-chrome {
+  @apply backdrop-blur-xl backdrop-saturate-150;
+  background: color-mix(in oklab, var(--surface) 88%, transparent);
+  border: 1px solid var(--hairline);
+  box-shadow: var(--shadow-card);
+}
+.dark .study-chrome {
+  border-color: var(--hairline-soft);
 }
 
 .card {