docs(e2e): note native Linux support and E2E_PORT

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dev/e2e/README.md

@@ -14,6 +14,11 @@ Log in from the app with **server** `http://10.0.2.2:8090` (Android
 emulator) or `http://127.0.0.1:8090` (Expo web / `adb reverse tcp:8090 tcp:8090`),
 **user** `e2e`, **password** `E2eTest#2026pass`.
 
+Runs on native Linux (cargo, curl, ffmpeg with `drawtext`, exiftool) or in
+WSL driving the Windows toolchain; the script detects which. If port 8090 is
+taken, pick another with `E2E_PORT=8091` (the app's `drive-app` skill reads
+the same variable).
+
 ## Isolation
 
 It runs next to a real local server without touching it: