fix(brain): route auxiliary small-model calls to an available model

The config template never set intent_judge_model, so it fell back to the code
default gemma4:e2b. That model is not pulled by this stack (Ollama only has
qwen2.5:3b, qwen3:8b, nomic-embed-text), so every auxiliary small-model call —
intent judge, tool router, weather place extraction, query decomposition —
targeted a non-existent model, silently failed, and fell open. This crippled
tool routing and argument extraction on the 3B brain.

Render intent_judge_model from a new OLLAMA_INTENT_MODEL env var that defaults
to OLLAMA_CHAT_MODEL, so the auxiliary calls reuse the already-warm chat model
(one resident model, no extra load). tool_router_model="" then resolves through
the chain to the same model.

Verified: rendered jarvis.json now has intent_judge_model=qwen2.5:3b, and the
weather place extractor returns "서울" / "Tokyo" (it returned None for
everything while pointed at the missing gemma4:e2b).

.env.example

@@ -56,6 +56,13 @@ OLLAMA_BASE_URL=http://127.0.0.1:11434
 # Korean on factual/tool replies; can occasionally leak a trailing CJK phrase on
 # free-form chit-chat. Swap back to qwen3:8b for the strongest tool-calling.
 OLLAMA_CHAT_MODEL=qwen2.5:3b
+# Model for the auxiliary small-model calls: intent judge, tool router, weather
+# place extraction, query decomposition. BLANK (default) reuses OLLAMA_CHAT_MODEL
+# so the stack runs on one already-warm model. The code's built-in default
+# (gemma4:e2b) is NOT pulled by this stack, so leaving this unset previously made
+# every router/extractor call silently fail. Only set this if you also pull the
+# model into Ollama.
+OLLAMA_INTENT_MODEL=
 OLLAMA_EMBED_MODEL=nomic-embed-text
 WHISPER_MODEL=small