feat(desktop): unified overlay design system, BrandMark & onboarding redesign (#40708)

* fix(desktop): unify dialog/overlay buttons on shared Button component

Replace raw <button> action/text controls across the modal layer (boot
failure, install, update, onboarding, clarify, model-visibility,
notifications, gateway menu) with the shared Button + its variants
(text / ghost / icon-xs). Drops the bespoke square-cornered styling so
every dialog matches the app's slightly-rounded button system, and
swaps clarify-tool's hardcoded "Skip" for the existing i18n string.

* feat(desktop): add dev-only dialog gallery for auditing overlays

A code-split, DEV-gated harness (toggle ⌘/Ctrl+Alt+Shift+D) that triggers
every dialog/overlay so their buttons can be eyeballed in one place:
store-driven overlays (boot failure, updates, notifications, sudo/secret)
plus in-place dialogs (confirm, profile create/rename, attach-url, model
picker/visibility, clarify, tool approval). Never ships to production.

* fix(desktop): use Ctrl+Shift+D for dialog gallery (mac-friendly)

The Cmd/Ctrl+Alt+Shift+D chord is impractical on macOS (Option mangles
the keypress). Ctrl+Shift+D is the same chord on every platform and uses
neither Cmd nor Option.

* fix(desktop): stop overriding button icon size to size-4

Action buttons hardcoded size-4 icons, overriding the Button component's
built-in size-3.5. That extra 2px is why boot-failure / onboarding / gateway
buttons looked chunkier than the settings "Apply" (size-3.5 spinner) despite
being the same component+size. Drop the overrides so icons inherit 3.5.

* feat(desktop): add BrandMark, use it in the updates overlay hero

New BrandMark renders the white logo.png on a hardcoded brand-blue tile
(#0000F2 light / #222 dark), replacing the generic Sparkles hero glyph in
the "update available" overlay. Trying it here first to iterate on the look.

NOTE: apps/desktop/public/logo.png is currently a 1x1 placeholder — the tile
renders now; the glyph appears once the real white logo art is dropped in.

* feat(desktop): add real logo.png asset, render it white in BrandMark

logo.png is blue line-art on transparent, so force it white via filter to
read on both the brand-blue (#0000F2) and near-black (#222) tiles. Bump the
glyph to 62% of the tile for the portrait aspect.

* fix(desktop): BrandMark renders logo as-is, no light bg/radius/padding

Drop the white filter, the hardcoded light-mode blue tile, the radius, and
the inner padding. Logo now fills the tile over a transparent surface in
light mode; dark keeps the #222 tile.

* fix(desktop): bump updates-overlay BrandMark to size-16

* feat(desktop): use downscaled karb.webp in BrandMark

Swap the BrandMark glyph to karb.webp, downscaled from 1129x1418/888KB to
254x320/81KB for the hero badge.

* feat(desktop): use nous-girl mark in BrandMark, invert in dark

Key the white background to transparent so only the black line-art remains
(384px/20KB webp). Light mode shows black art; dark mode flips it white via
dark:invert on the #222 tile. Drop the now-unused karb.webp and logo.png.

* fix(desktop): BrandMark uses nous-girl as-is (no transparent/invert)

The dark-mode invert read as a creepy negative. Use the opaque black-on-white
mark unchanged in both themes; drop the white-key, dark:invert, and #222 tile.

* fix(desktop): give BrandMark an explicit white bg tile

* fix(desktop): use nous-girl.jpg directly in BrandMark

* perf(desktop): downscale nous-girl.jpg to 256x256 (466KB -> 19KB)

* style(desktop): bump nous light --theme-secondary to 14% blue

* fix(desktop): outline button is transparent, not chrome-filled

The outline variant used bg-background (the chrome color), so on cards/overlays
with a different surface it rendered as an odd gray-blue fill (visible on the
boot overlay's Repair install / Use local gateway). Make it bg-transparent so
it inherits the surface like a real outline. Reverts the unrelated
--theme-secondary tweak.

* fix(desktop): clean outline button — thin border, no shadow/fill

Drop shadow-xs and the resting fills (light chrome bg, dark bg-input/30) so
outline is just a thin clean border with a subtle hover, in both themes.

* fix(desktop): stop forcing tertiary bg on outline buttons

A global [data-variant='outline'] rule set background: var(--ui-bg-tertiary),
which (attribute-selector specificity) overrode the cva bg-transparent — so
outline buttons always showed the pale tertiary fill on cards/overlays
regardless of the variant classes. Scope that fill to secondary only; outline
is now a true transparent border.

* style(desktop): unified overlay design system + restore #38631 flat-UI

Overlays/dialogs/toasts share a custom shadow-nous (downward-weighted) and
--stroke-nous hairline instead of hard borders: boot-failure, install,
notifications, model-picker, onboarding, prompt-overlays, updates, Dialog.

- button: outline is a 1px inset ring (no fill/shadow); chrome lives in Button
- BrandMark: 256px nous-girl mark replaces sparkle glyphs (updates/onboarding/about)
- onboarding: conditional header, lemniscate-bloom loaders, OTP device-code boxes,
  NOUS CONNECTED hero (ascii decode) + cuneiform easter egg, "Begin" matrix exit
- shared LogView + ErrorState; math/ascii loaders over "Loading..." text
- appearance-settings flattened to SegmentedControl/ListRow; keybind-panel on
  shadow-nous + text-variant reset
- restore flat-UI clobbered by #38631's stale-squash (4a1907bd1): command-center,
  profiles, skills, messaging, cron de-boxed; shared SearchField + PAGE_INSET_X;
  profiles back on OverlaySplitLayout; skills tabs+search one row, no row dividers

* refactor(desktop): clean pass — drop dead code, dedupe, fix stale docs

- log-view: drop unused `bare` prop + forwardRef (no caller uses ref)
- install-overlay: drop `stateOverride` (only the removed dev gallery used it)
- profiles: ProfilesViewProps down to { onClose } (drop vestigial section/titlebar)
- onboarding: hoist shared PROVIDER_ROW_CLASS (was duplicated 2x)
- brand-mark / error-state: tighten comments, fix stale AlertCircle reference

apps/desktop/src/components/notifications.tsx

@@ -3,6 +3,7 @@ import { type ReactNode, useEffect, useRef, useState } from 'react'
 import { createPortal } from 'react-dom'
 
 import { Alert, AlertDescription, AlertTitle } from '@/components/ui/alert'
+import { Button } from '@/components/ui/button'
 import { Codicon } from '@/components/ui/codicon'
 import { CopyButton } from '@/components/ui/copy-button'
 import { useI18n } from '@/i18n'
@@ -26,8 +27,7 @@ const tone: Record<NotificationKind, { icon: IconComponent; iconClass: string; v
   success: { icon: CheckCircle2, iconClass: 'text-primary', variant: 'success' }
 }
 
-const STACK_SURFACE = 'pointer-events-auto border-border/80 bg-popover/95 shadow-lg shadow-black/5 backdrop-blur-md'
-const GHOST_BTN = 'bg-transparent text-muted-foreground hover:text-foreground'
+const STACK_SURFACE = 'pointer-events-auto border border-(--stroke-nous) bg-popover/95 shadow-nous backdrop-blur-md'
 
 export function NotificationStack() {
   const notifications = useStore($notifications)
@@ -83,12 +83,12 @@ export function NotificationStack() {
       {expanded && olderNotifications.map(n => <NotificationItem key={n.id} notification={n} />)}
       {overflowCount > 0 && (
         <div className={cn(STACK_SURFACE, 'flex min-h-8 items-center justify-between rounded-lg px-3 text-xs')}>
-          <button className={cn(GHOST_BTN, 'font-medium')} onClick={() => setExpanded(v => !v)} type="button">
+          <Button className="-ml-2 font-medium" onClick={() => setExpanded(v => !v)} size="xs" type="button" variant="text">
             {expanded ? copy.hide : copy.show} {copy.more(overflowCount)}
-          </button>
-          <button className={GHOST_BTN} onClick={clearNotifications} type="button">
+          </Button>
+          <Button className="-mr-2" onClick={clearNotifications} size="xs" type="button" variant="text">
             {copy.clearAll}
-          </button>
+          </Button>
         </div>
       )}
     </div>,
@@ -117,27 +117,31 @@ function NotificationItem({ notification }: { notification: AppNotification }) {
           <p className="m-0">{notification.message}</p>
           {hasDetail && <NotificationDetail detail={notification.detail || ''} />}
           {notification.action && (
-            <button
-              className="mt-1.5 inline-flex items-center rounded-md bg-primary/15 px-2 py-1 text-xs font-medium text-primary transition-colors hover:bg-primary/25"
+            <Button
+              className="mt-1.5 bg-primary/15 font-medium text-primary hover:bg-primary/25 hover:text-primary"
               onClick={() => {
                 notification.action?.onClick()
                 dismissNotification(notification.id)
               }}
+              size="xs"
               type="button"
+              variant="ghost"
             >
               {notification.action.label}
-            </button>
+            </Button>
           )}
         </AlertDescription>
       </div>
-      <button
+      <Button
         aria-label={copy.dismiss}
-        className="col-start-3 -mr-1 grid size-6 place-items-center rounded-md bg-transparent text-muted-foreground transition-colors hover:bg-accent hover:text-foreground"
+        className="col-start-3 -mr-1 text-muted-foreground"
         onClick={() => dismissNotification(notification.id)}
+        size="icon-xs"
         type="button"
+        variant="ghost"
       >
         <Codicon name="close" size="0.875rem" />
-      </button>
+      </Button>
     </Alert>
   )
 }
@@ -149,7 +153,7 @@ function NotificationDetail({ detail }: { detail: string }) {
   return (
     <details className="mt-2 text-xs text-muted-foreground">
       <summary className="select-none font-medium text-muted-foreground hover:text-foreground">{copy.details}</summary>
-      <div className="mt-1 rounded-md border border-border/70 bg-background/65 p-2">
+      <div className="mt-1 rounded-md bg-background/65 p-2">
         <pre className="max-h-32 whitespace-pre-wrap wrap-break-word font-mono text-[0.6875rem] leading-relaxed">
           {detail}
         </pre>