feat: P3 final batch - zoom, fonts, dark mode, tech debt cleanup

- Page zoom control (0.5-2.0x, localStorage)
- Custom monospace font selector (6 presets + custom)
- Element Plus dark mode final fixes (dropdown, message-box, switch, popper)
- AGENTS.md updated with correct paths + new modules/components/IPC channels
- ROADMAP: window state persistence already done via win-state.ts
- ROADMAP: tech debt items marked done

src/stores/app.ts

@@ -9,6 +9,8 @@ export const useAppStore = defineStore('app', () => {
   const isDark = ref(true)
   const fontSize = ref<number>(Number(localStorage.getItem('fontSize')) || 13)
   const scanCount = ref<number>(Number(localStorage.getItem('scanCount')) || 100)
+  const zoom = ref<number>(Number(localStorage.getItem('zoom')) || 1.0)
+  const fontFamily = ref<string>(localStorage.getItem('fontFamily') || 'Cascadia Code')
 
   function applyTheme(mode: ThemeMode, osDark?: boolean) {
     theme.value = mode
@@ -45,5 +47,21 @@ export const useAppStore = defineStore('app', () => {
     localStorage.setItem('scanCount', String(count))
   }
 
-  return { theme, isDark, fontSize, scanCount, setTheme, setFontSize, setScanCount }
+  function setZoom(value: number) {
+    zoom.value = value
+    localStorage.setItem('zoom', String(value))
+    document.body.style.zoom = String(value)
+  }
+
+  function setFontFamily(value: string) {
+    fontFamily.value = value
+    localStorage.setItem('fontFamily', value)
+    document.documentElement.style.setProperty('--font-mono', value)
+  }
+
+  // Apply saved zoom and fontFamily on mount
+  document.body.style.zoom = String(zoom.value)
+  document.documentElement.style.setProperty('--font-mono', fontFamily.value)
+
+  return { theme, isDark, fontSize, scanCount, zoom, fontFamily, setTheme, setFontSize, setScanCount, setZoom, setFontFamily }
 })