feat: implement three-mode UI system (Easy / Pro / Chat)

Add switchable UI modes with conditional rendering:
- Easy mode: goal-based interface with 7 guided workflows
- Pro mode: current technical interface preserved with Quick Start Goals
- Chat mode: AIUI placeholder for future integration

New components: ModeSwitcher, EasyHome, GoalDetail wizard, Chat placeholder
New stores: uiMode (mode persistence), goals (progress tracking)
New data: goal definitions catalog, helpTree goals section
Modified: Dashboard (reactive nav), Home (mode dispatcher), Settings (mode picker),
Router (goal/chat routes), Spotlight (goal search integration)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/stores/uiMode.ts

@@ -0,0 +1,33 @@
+import { defineStore } from 'pinia'
+import { ref, computed } from 'vue'
+import type { UIMode } from '@/types/api'
+
+const STORAGE_KEY = 'archipelago-ui-mode'
+
+export const useUIModeStore = defineStore('uiMode', () => {
+  const mode = ref<UIMode>(loadFromStorage())
+
+  function loadFromStorage(): UIMode {
+    const stored = localStorage.getItem(STORAGE_KEY)
+    if (stored === 'gamer' || stored === 'easy' || stored === 'chat') return stored
+    return 'gamer'
+  }
+
+  function syncFromBackend(backendMode: UIMode | undefined) {
+    if (backendMode && ['gamer', 'easy', 'chat'].includes(backendMode)) {
+      mode.value = backendMode
+      localStorage.setItem(STORAGE_KEY, backendMode)
+    }
+  }
+
+  function setMode(newMode: UIMode) {
+    mode.value = newMode
+    localStorage.setItem(STORAGE_KEY, newMode)
+  }
+
+  const isGamer = computed(() => mode.value === 'gamer')
+  const isEasy = computed(() => mode.value === 'easy')
+  const isChat = computed(() => mode.value === 'chat')
+
+  return { mode, setMode, syncFromBackend, isGamer, isEasy, isChat }
+})