feat: local LLM via Ollama + structured output response_format

- Add setup script (scripts/setup-local-llm.sh) for one-command Ollama setup
  Mac: native Metal GPU, Linux: containerized via docker-compose profiles
- Add ollama-gpu and ollama-cpu docker-compose profiles for Linux
- Add extra_hosts to server/hatchet-worker-llm for host.docker.internal
- Pass response_format JSON schema in StructuredOutputWorkflow.extract()
  enabling grammar-based constrained decoding on Ollama/llama.cpp/vLLM/OpenAI
- Update .env.example with Ollama as default LLM option
- Add Ollama PRD and local dev setup docs

scripts/setup-local-llm.sh

@@ -0,0 +1,100 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+MODEL="${LLM_MODEL:-qwen2.5:14b}"
+OLLAMA_PORT="${OLLAMA_PORT:-11434}"
+
+wait_for_ollama() {
+    local url="$1"
+    local retries=30
+    for i in $(seq 1 "$retries"); do
+        if curl -sf "$url/api/tags" > /dev/null 2>&1; then
+            return 0
+        fi
+        echo "  Waiting for Ollama... ($i/$retries)"
+        sleep 2
+    done
+    echo "ERROR: Ollama not responding at $url after $retries attempts"
+    return 1
+}
+
+OS="$(uname -s)"
+
+case "$OS" in
+    Darwin)
+        echo "macOS detected -- Ollama must run natively for Metal GPU acceleration."
+        echo ""
+
+        if ! command -v ollama &> /dev/null; then
+            echo "Ollama not found. Install it first:"
+            echo "  brew install ollama"
+            echo "  # or download from https://ollama.com/download"
+            exit 1
+        fi
+
+        # Start Ollama if not already running
+        if ! curl -sf "http://localhost:$OLLAMA_PORT/api/tags" > /dev/null 2>&1; then
+            echo "Starting Ollama..."
+            ollama serve &
+            disown
+        else
+            echo "Ollama already running."
+        fi
+
+        wait_for_ollama "http://localhost:$OLLAMA_PORT"
+
+        echo "Pulling model $MODEL..."
+        ollama pull "$MODEL"
+
+        echo ""
+        echo "Done. Add to server/.env:"
+        echo "  LLM_URL=http://host.docker.internal:$OLLAMA_PORT/v1"
+        echo "  LLM_MODEL=$MODEL"
+        echo "  LLM_API_KEY=not-needed"
+        echo ""
+        echo "Then: docker compose up -d"
+        ;;
+
+    Linux)
+        echo "Linux detected."
+        echo ""
+
+        if command -v nvidia-smi &> /dev/null && nvidia-smi > /dev/null 2>&1; then
+            echo "NVIDIA GPU detected -- using ollama-gpu profile."
+            PROFILE="ollama-gpu"
+            LLM_URL="http://ollama:$OLLAMA_PORT/v1"
+        else
+            echo "No NVIDIA GPU -- using ollama-cpu profile."
+            PROFILE="ollama-cpu"
+            LLM_URL="http://ollama-cpu:$OLLAMA_PORT/v1"
+        fi
+
+        echo "Starting Ollama container..."
+        docker compose --profile "$PROFILE" up -d
+
+        # Determine container name
+        if [ "$PROFILE" = "ollama-gpu" ]; then
+            SVC="ollama"
+        else
+            SVC="ollama-cpu"
+        fi
+
+        wait_for_ollama "http://localhost:$OLLAMA_PORT"
+
+        echo "Pulling model $MODEL..."
+        docker compose exec "$SVC" ollama pull "$MODEL"
+
+        echo ""
+        echo "Done. Add to server/.env:"
+        echo "  LLM_URL=$LLM_URL"
+        echo "  LLM_MODEL=$MODEL"
+        echo "  LLM_API_KEY=not-needed"
+        echo ""
+        echo "Then: docker compose --profile $PROFILE up -d"
+        ;;
+
+    *)
+        echo "Unsupported OS: $OS"
+        exit 1
+        ;;
+esac