feat: add Quick Prompt global hotkey popup for one-off AI questions

Add a system-wide global hotkey (Win+Shift+A / Cmd+Shift+A) that summons
a floating, frameless popup window for quick AI interactions from any app.

Main process:
- GlobalHotkeyService for registering/unregistering system-wide shortcuts
- Frameless, transparent, always-on-top BrowserWindow factory
- IPC handlers for send, discard, close, continue-in-aryx, cancel
- Session event routing from sidecar to quick prompt window
- Settings persistence for default model, hotkey, and reasoning effort

Renderer (separate lightweight entry):
- QuickPromptApp with session state, streaming, keyboard shortcuts
- QuickPromptInput with model selector trigger and cancel support
- QuickPromptResponse with streamed markdown and thinking blocks
- QuickPromptActions (Discard / Close / Continue in Aryx)
- ModelSelector dropdown with tier badges and reasoning effort
- Glass Command Bar aesthetic with animated gradient border

Settings:
- Quick Prompt section in SettingsPanel with enable toggle, hotkey
  display, default model selector, and reasoning effort picker

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/windows/createQuickPromptWindow.ts

@@ -0,0 +1,89 @@
+import electron from 'electron';
+import type { BrowserWindow as BrowserWindowType } from 'electron';
+import { join } from 'node:path';
+
+import { resolveWindowIconPath } from '@main/windows/appIcon';
+
+const { app, BrowserWindow, screen } = electron;
+
+export function createQuickPromptWindow(): BrowserWindowType {
+  const window = new BrowserWindow({
+    width: 680,
+    height: 72,
+    show: false,
+    frame: false,
+    transparent: true,
+    resizable: false,
+    skipTaskbar: true,
+    alwaysOnTop: true,
+    maximizable: false,
+    minimizable: false,
+    fullscreenable: false,
+    title: 'Aryx Quick Prompt',
+    icon: resolveWindowIconPath({
+      appPath: app.getAppPath(),
+      platform: process.platform,
+    }),
+    webPreferences: {
+      preload: join(__dirname, '../preload/quickprompt.js'),
+      contextIsolation: true,
+      nodeIntegration: false,
+    },
+  });
+
+  const rendererUrl = process.env.ELECTRON_RENDERER_URL;
+
+  if (rendererUrl) {
+    void window.loadURL(`${rendererUrl}/quickprompt.html`);
+  } else {
+    void window.loadFile(join(__dirname, '../../dist/renderer/quickprompt.html'));
+  }
+
+  window.on('blur', () => {
+    if (window.isVisible()) {
+      window.webContents.send('quick-prompt:hide');
+      window.hide();
+    }
+  });
+
+  return window;
+}
+
+export function toggleQuickPromptWindow(window: BrowserWindowType): void {
+  if (window.isVisible()) {
+    window.webContents.send('quick-prompt:hide');
+    window.hide();
+    return;
+  }
+
+  centerOnActiveDisplay(window);
+  window.webContents.send('quick-prompt:show');
+  window.show();
+  window.focus();
+}
+
+export function showQuickPromptWindow(window: BrowserWindowType): void {
+  centerOnActiveDisplay(window);
+  window.webContents.send('quick-prompt:show');
+  window.show();
+  window.focus();
+}
+
+export function hideQuickPromptWindow(window: BrowserWindowType): void {
+  if (!window.isVisible()) return;
+  window.webContents.send('quick-prompt:hide');
+  window.hide();
+}
+
+function centerOnActiveDisplay(window: BrowserWindowType): void {
+  const cursorPoint = screen.getCursorScreenPoint();
+  const activeDisplay = screen.getDisplayNearestPoint(cursorPoint);
+  const { x, y, width, height } = activeDisplay.workArea;
+
+  const [windowWidth] = window.getSize();
+  const windowX = Math.round(x + (width - windowWidth) / 2);
+  // Position in the upper-third of the screen for command-bar feel
+  const windowY = Math.round(y + height * 0.25);
+
+  window.setPosition(windowX, windowY);
+}