All ~165 legacy var() usages (--color-*, --surface*, --accent*, --border,
--text*) with hex fallbacks and ~150 raw hex literals across app.scss and
24 scoped style blocks are swapped to the kit's --gn-* tokens per the
intent of the old fallback values:

- accent/primary/teal (#7aa2f7/#4ec9b0) -> --gn-color-secondary
- amber/orange highlights -> --gn-color-accent
- text greys -> --gn-color-text-{light,medium,dark}
- panels -> --gn-surface-panel; elevated tints -> color-mix over panel
- translucent overlays -> color-mix(in srgb, ..., transparent)

Deliberately literal: terminal deep bg #0f0f14 (darker than any token)
and the content-card image badge teal #89dceb (kit has no teal). File
type badges keep a categorical palette via nearest kit tokens.

Dead "UI kit overrides" block halved: kit 1.0 dropped hover icon
rotation, so only the app-owned chevron open-state flip remains.

Verified: vitest 111 passed, build OK, dev render matches W1 baseline

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gnexus-ui-kit's iconNode() does not prepend the base `ph` class
when the icon string starts with `ph-`; it only keeps the string
as-is. All icon props must include the base class explicitly:
`icon="ph ph-sidebar"` instead of `icon="ph-sidebar"`.

Updated 15 icon bindings across 9 components.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

- Update vendor/gnexus-ui-kit to v0.2.0 (Vue components + composables)
- Add Vite aliases for gnexus-ui-kit/vue and gnexus-ui-kit/css
- Install GnexusUiVue plugin in main.js + GnToastProvider in App.vue
- Migrate ProfileBadge → GnBadge
- Migrate ErrorMessage → GnAlert
- Migrate ConfirmDialog → GnConfirmDialog
- Migrate raw <button> elements → GnButton / GnIconButton in:
  WelcomeScreen, LoginScreen, ChatArea, ChatHeader, AppSidebar,
  ArtifactsPanel, UserMessage, AssistantMessage, SelectionToolbar

Build and tests pass (51/51).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

- Backend: new endpoint GET /auth/status returns {configured: bool}
- Webclient auth store: add authConfigured ref + fetchStatus()
- LoginScreen.vue: centered card with logo, title, and login button
- App.vue: show LoginScreen overlay when auth is configured but
  user is not authenticated (z-index 9999, blocks all UI)
- App.vue onMounted: fetch auth status before trying to resolve user

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>