Frutiger Aero theme, pixel-measured contrast fixes, sheet surfaces

Frutiger Aero (Settings -> Theme): a third theme, not a dark/light variant.
A sky gradient with a strip of grass, the glacier blobs become clouds, the
orbs soap bubbles, glass gets the classic horizon gloss and the buttons a
glossy aqua. The light/dark toggles (header, rail, chat header) hide while it
is on and the picker says why; the pre-paint script applies the class before
first paint and the PWA status bar follows (#3fa3e0). Its muted/frost text is
darker than Light's because those labels sit directly on the sky.

Contrast, measured on real pixels (tests/contrast.mjs, now covering aero):
- The light settings sheet was translucent over a dark scrim, so its muted
  text measured ~2.8:1. Sheets and dialogs now use --glass-sheet-bg (a more
  opaque surface), and Light's --text-muted is a touch darker.
- Result: 0 below-minimum findings and 0 axe violations across every screen,
  all three themes, phone and desktop.

Also: the suites now seed the cookie notice as already dismissed (they run as
a returning user); the regression suite opts out to test the notice itself —
the previous deploy failed its gate because the notice blocked a chat chip
click. The notice also hides during immersive sessions (overlay-open), so it
can never cover a study feed.

Version 0.1.8, SW -> freezmo-v54.

components/SettingsDialog.tsx

@@ -12,6 +12,7 @@ import { springSheet } from "@/lib/motion";
 import { ModelErrorActions } from "@/components/ModelErrorActions";
 import { DataSection } from "@/components/DataSection";
 import { LearningSection } from "@/components/LearningSection";
+import { ThemeSection } from "@/components/ThemeSection";
 import { SyncSection } from "@/components/SyncSection";
 import { clearApiKey, saveSettings, settingsStore } from "@/lib/settings";
 import { useBackClose } from "@/lib/use-back-close";
@@ -203,7 +204,7 @@ export function SettingsDialog({
             exit={reduceMotion ? { opacity: 0 } : phone ? { y: "100%", opacity: 0 } : { y: 32, opacity: 0 }}
             transition={phone ? springSheet : { type: "spring", stiffness: 340, damping: 32 }}
             onClick={(event) => event.stopPropagation()}
-            className="glass-panel relative flex max-h-[90dvh] w-full max-w-lg flex-col overflow-hidden rounded-t-[1.6rem] shadow-2xl sm:rounded-[1.35rem]"
+            className="glass-panel glass-sheet relative flex max-h-[90dvh] w-full max-w-lg flex-col overflow-hidden rounded-t-[1.6rem] shadow-2xl sm:rounded-[1.35rem]"
           >
             {/* handle + header: the drag strip. Fixed, so the body scrolls. */}
             <div
@@ -407,8 +408,13 @@ export function SettingsDialog({
                       />
                     </section>
 
-                    {/* ------------------------------------------- data & sync */}
+                    {/* ------------------------------------------- theme */}
+                    <ThemeSection />
+
+                    {/* ----------------------------------------- learning */}
                     <LearningSection level={3} />
+
+                    {/* ------------------------------------------- data & sync */}
                     <DataSection />
                     <SyncSection />
 
@@ -764,8 +770,13 @@ export function SettingsDialog({
                   />
                 </section>
 
-                {/* ------------------------------------------- data & sync */}
+                {/* ------------------------------------------- theme */}
+                <ThemeSection />
+
+                {/* ----------------------------------------- learning */}
                 <LearningSection level={3} />
+
+                {/* ------------------------------------------- data & sync */}
                 <DataSection />
                 <SyncSection />