Initial commit: DJ Visualizer

Electron app with audio-reactive fractal/abstract visuals on an external
display. Dual-window setup (control panel + fullscreen output), 8 WebGL
scenes, audio from file/live input/system audio, image and scrolling-text
overlays.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

preload.js

@@ -0,0 +1,24 @@
+const { contextBridge, ipcRenderer, webUtils } = require('electron');
+
+// Each window is launched with --role=control or --role=output.
+const roleArg = process.argv.find(a => a.startsWith('--role='));
+const role = roleArg ? roleArg.split('=')[1] : 'control';
+
+contextBridge.exposeInMainWorld('djv', {
+  role,
+  // Control -> Output commands.
+  send: (msg) => ipcRenderer.send('ctl', msg),
+  onControl: (cb) => ipcRenderer.on('ctl', (_e, m) => cb(m)),
+  // Output -> Control reports.
+  report: (msg) => ipcRenderer.send('rpt', msg),
+  onReport: (cb) => ipcRenderer.on('rpt', (_e, m) => cb(m)),
+  // Display management (control window).
+  // Resolve a dropped/picked File to its absolute filesystem path.
+  pathForFile: (file) => {
+    try { return webUtils.getPathForFile(file); }
+    catch (e) { return file && file.path ? file.path : null; }
+  },
+  listDisplays: () => ipcRenderer.invoke('displays:list'),
+  moveOutputTo: (id) => ipcRenderer.invoke('output:moveTo', id),
+  toggleOutputFullscreen: () => ipcRenderer.invoke('output:toggleFullscreen')
+});