feat: CEF mode for Electrobun E2E — CDP automation, WebGL unlocked

- electrobun.config.ts: AGOR_CEF=1 enables bundleCEF + chromiumFlags
  (remote-debugging-port=9222). Production stays on WebKitGTK.
- wdio.electrobun.conf.js: rewritten for CDP via devtools protocol.
  Spawns app, waits for CDP port, kills on complete.
- helpers/actions.ts: waitForPort() polls CDP /json endpoint
- docs/testing.md: CEF mode docs, CI setup, troubleshooting
- npm script: test:e2e:electrobun prepends AGOR_CEF=1

CEF also enables: WebGL xterm.js addon (unlimited terminals),
WebGPU, full Chrome DevTools — all for dev/test only.

ui-electrobun/electrobun.config.ts

@@ -1,5 +1,15 @@
 import type { ElectrobunConfig } from "electrobun";
 
+// CEF mode: opt-in via AGOR_CEF=1. Used for dev/test (E2E automation via CDP,
+// WebGL support, unlimited xterm instances). Production uses WebKitGTK (lighter,
+// no Chromium dependency, system-native).
+const useCEF = process.env.AGOR_CEF === "1";
+
+// When CEF is active, enable remote debugging for CDP-based E2E automation.
+const cefFlags: Record<string, string | boolean> | undefined = useCEF
+	? { "remote-debugging-port": "9222", "remote-allow-origins": "*" }
+	: undefined;
+
 export default {
 	app: {
 		name: "Agent Orchestrator",
@@ -16,16 +26,22 @@ export default {
 		},
 		watchIgnore: ["dist/**"],
 		mac: {
-			bundleCEF: false,
+			bundleCEF: useCEF,
 			bundleWGPU: true,
+			...(useCEF && { defaultRenderer: "cef" as const }),
+			...(cefFlags && { chromiumFlags: cefFlags }),
 		},
 		linux: {
-			bundleCEF: false,
+			bundleCEF: useCEF,
 			bundleWGPU: true,
+			...(useCEF && { defaultRenderer: "cef" as const }),
+			...(cefFlags && { chromiumFlags: cefFlags }),
 		},
 		win: {
-			bundleCEF: false,
+			bundleCEF: useCEF,
 			bundleWGPU: true,
+			...(useCEF && { defaultRenderer: "cef" as const }),
+			...(cefFlags && { chromiumFlags: cefFlags }),
 		},
 	},
 } satisfies ElectrobunConfig;