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.

tests/test_tool_router_resolution.py

@@ -0,0 +1,63 @@
+"""Tests for tool-router model resolution order.
+
+The reply engine and the listener warmup path both need to pick the model
+used for LLM-based tool selection, and they MUST pick the same one — if they
+diverge, warmup loads the wrong model and the first real routing call eats a
+cold-start stall. The resolution order is enforced by a single helper
+(``resolve_tool_router_model``), which this test exercises directly.
+
+Order: `tool_router_model` → `intent_judge_model` → `ollama_chat_model` →
+empty string. The key property is that an explicit `tool_router_model` wins
+over everything, and that an empty `tool_router_model` falls through to the
+(small, fast, already-warm) judge model BEFORE the (large, slow) chat model.
+"""
+
+import pytest
+
+from jarvis.reply.engine import resolve_tool_router_model
+
+
+class _Cfg:
+    """Minimal cfg stand-in with only the attributes the resolver reads."""
+
+    def __init__(self, router="", judge="", chat=""):
+        self.tool_router_model = router
+        self.intent_judge_model = judge
+        self.ollama_chat_model = chat
+
+
+class TestToolRouterModelResolution:
+
+    @pytest.mark.unit
+    def test_explicit_router_wins(self):
+        cfg = _Cfg(router="custom-router", judge="judge-m", chat="chat-m")
+        assert resolve_tool_router_model(cfg) == "custom-router"
+
+    @pytest.mark.unit
+    def test_empty_router_falls_through_to_judge(self):
+        """The whole point of the helper: an unset tool_router_model must
+        pick the judge model, not the chat model. This is what keeps the
+        routing call on the small, warm model instead of reloading the
+        large chat model every turn."""
+        cfg = _Cfg(router="", judge="judge-m", chat="chat-m")
+        assert resolve_tool_router_model(cfg) == "judge-m"
+
+    @pytest.mark.unit
+    def test_falls_through_to_chat_when_no_router_or_judge(self):
+        cfg = _Cfg(router="", judge="", chat="chat-m")
+        assert resolve_tool_router_model(cfg) == "chat-m"
+
+    @pytest.mark.unit
+    def test_returns_empty_when_nothing_configured(self):
+        """The caller handles an empty model name by falling back to the
+        all-tools path — the helper itself should not invent a default."""
+        cfg = _Cfg(router="", judge="", chat="")
+        assert resolve_tool_router_model(cfg) == ""
+
+    @pytest.mark.unit
+    def test_robust_to_missing_attributes(self):
+        """When a cfg-like object is missing an attribute entirely (as can
+        happen for partial mocks), the resolver must not raise."""
+        class Partial:
+            ollama_chat_model = "only-chat"
+        assert resolve_tool_router_model(Partial()) == "only-chat"