feat(desktop): global Cmd+K palette + UI consistency overhaul

Builds on the clarify/needs-input work with a cross-cutting pass to make
the desktop surfaces feel like one app.

- Global Cmd+K command palette (cmdk): nav, settings deep-links, async
  API-key / MCP-server / archived-session groups, reusable theme sub-page
  (light/dark groups, stays open on pick), loop nav, fuzzy match. Replaces
  per-page settings search.
- Shared SearchField: borderless, underline-on-focus, `field-sizing`
  auto-width. Unifies sessions sidebar, pages, overlays, command center,
  cron; drops bespoke OverlaySearchInput.
- Cron & Profiles converted to OverlayView; flat token-driven panels
  (no card-in-card / divider borders) matching command center.
- `r` refresh hotkey via useRefreshHotkey; drop the visible refresh buttons.
- Button text/textStrong link variants applied across settings & views;
  shared PAGE_INSET_X content gutters.
- Math/ascii loaders replace "Loading…" text placeholders; x-icon close
  over text "Close"; cursor-pointer at the dropdown/select primitive level.

apps/desktop/src/app/right-sidebar/files/tree.tsx

@@ -1,6 +1,7 @@
 import { useCallback, useRef, useState } from 'react'
 import { type NodeApi, type NodeRendererProps, Tree, type TreeApi } from 'react-arborist'
 
+import { PageLoader } from '@/components/page-loader'
 import { Codicon } from '@/components/ui/codicon'
 import { useResizeObserver } from '@/hooks/use-resize-observer'
 import { cn } from '@/lib/utils'
@@ -121,11 +122,7 @@ export function ProjectTree({
 }
 
 function TreeSizingState() {
-  return (
-    <div className="flex h-full min-h-24 items-center justify-center px-3 text-[0.68rem] text-(--ui-text-tertiary)">
-      Loading files...
-    </div>
-  )
+  return <PageLoader aria-label="Loading files" className="min-h-24 px-3" />
 }
 
 function ProjectTreeRow({