Add Discord-native hybrid front-end for Jarvis (bot + bridge)

Transform isair/jarvis into a Discord-controlled voice assistant running on
the Ubuntu VNC desktop, keeping the mature ~39k-line Python brain intact.

- bot/ (Node + bun, discord.js): /자비스 slash commands (ephemeral),
  voice channel join + voice receive/playback, pluggable VNC screen broadcast
  (selfbot live / noVNC / screenshot)
- bridge/ (Python, Flask): wraps jarvis STT + run_reply_engine + Piper TTS
  behind a thin localhost HTTP API
- .env.example, scripts/ (start_bridge/start_bot/dev), README rewrite,
  docs/language-comparison.md and docs/vnc-xfce-setup.md

Language decision: hybrid (Python brain + Node/bun Discord layer) because
Discord blocks bot video; native screen broadcast only works via a Node
selfbot library.

.github/workflows/tests.yml

@@ -0,0 +1,28 @@
+name: tests
+
+on:
+  pull_request:
+  push:
+    branches: [ main, develop ]
+
+jobs:
+  unit:
+    name: Unit tests (Linux, Python 3.11)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-python@v6
+        with:
+          python-version: '3.11'
+          cache: pip
+          cache-dependency-path: requirements.txt
+      - name: Install system dependencies
+        run: sudo apt-get update && sudo apt-get install -y portaudio19-dev libegl1 libxkbcommon0
+      - name: Install deps
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install -r requirements.txt
+      - name: Run unit tests
+        run: |
+          python -m pytest -q -m unit
+