feat: WP-0003 — RoutingPolicy (FR-2) and HTTP serve mode (FR-1)

FR-2 RoutingPolicy:
- RoutingPolicy + RoutingRule dataclasses in llm_connect/routing.py
- resolve(task_type, estimated_cost_per_1k=None) with cost-cap fallback
- Exported from llm_connect.__init__; contract doc at contracts/functional/routing-policy.md
- 11 tests covering rule match, cost-cap, fallback, unknown type, no-match

FR-1 HTTP serve mode:
- LLMServer in llm_connect/server.py (stdlib http.server, zero extra deps)
- POST /execute + GET /health; CLI via python -m llm_connect.server
- [server] optional-dep group added to pyproject.toml
- Contract doc at contracts/functional/server.md
- 9 tests: health, round-trip, 400/404/500 errors, config forwarding
- Added "mock" provider to factory for CLI default

All 101 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_server.py

@@ -0,0 +1,134 @@
+"""
+Tests for LLMServer HTTP serve mode (FR-1).
+"""
+
+import json
+import urllib.error
+import urllib.request
+
+import pytest
+
+from llm_connect.adapter import MockLLMAdapter, ErrorLLMAdapter
+from llm_connect.models import RunConfig
+from llm_connect.server import LLMServer
+
+
+@pytest.fixture()
+def server():
+    """Start a server on a free port; stop after each test."""
+    s = LLMServer(adapter=MockLLMAdapter(mock_response="hello world"), port=0)
+    s.start()
+    yield s
+    s.stop()
+
+
+def _get(url: str) -> tuple[int, dict]:
+    try:
+        with urllib.request.urlopen(url) as resp:
+            return resp.status, json.loads(resp.read())
+    except urllib.error.HTTPError as exc:
+        return exc.code, json.loads(exc.read())
+
+
+def _post(url: str, body: dict) -> tuple[int, dict]:
+    payload = json.dumps(body).encode()
+    req = urllib.request.Request(
+        url,
+        data=payload,
+        headers={"Content-Type": "application/json"},
+        method="POST",
+    )
+    try:
+        with urllib.request.urlopen(req) as resp:
+            return resp.status, json.loads(resp.read())
+    except urllib.error.HTTPError as exc:
+        return exc.code, json.loads(exc.read())
+
+
+class TestHealth:
+    def test_health_returns_200(self, server):
+        status, body = _get(f"http://127.0.0.1:{server.port}/health")
+        assert status == 200
+        assert body["status"] == "ok"
+
+    def test_unknown_get_returns_404(self, server):
+        status, body = _get(f"http://127.0.0.1:{server.port}/nope")
+        assert status == 404
+
+
+class TestExecute:
+    def test_post_execute_round_trip(self, server):
+        status, body = _post(
+            f"http://127.0.0.1:{server.port}/execute",
+            {"prompt": "say hello"},
+        )
+        assert status == 200
+        assert body["content"] == "hello world"
+        assert body["finish_reason"] == "stop"
+
+    def test_response_includes_usage(self, server):
+        status, body = _post(
+            f"http://127.0.0.1:{server.port}/execute",
+            {"prompt": "count tokens"},
+        )
+        assert status == 200
+        assert "usage" in body
+        assert body["usage"]["total_tokens"] > 0
+
+    def test_missing_prompt_returns_400(self, server):
+        status, body = _post(
+            f"http://127.0.0.1:{server.port}/execute",
+            {"config": {}},
+        )
+        assert status == 400
+        assert "prompt" in body["error"]
+
+    def test_invalid_json_returns_400(self, server):
+        req = urllib.request.Request(
+            f"http://127.0.0.1:{server.port}/execute",
+            data=b"not json",
+            headers={"Content-Type": "application/json"},
+            method="POST",
+        )
+        try:
+            with urllib.request.urlopen(req) as resp:
+                status, body = resp.status, json.loads(resp.read())
+        except urllib.error.HTTPError as exc:
+            status, body = exc.code, json.loads(exc.read())
+        assert status == 400
+
+    def test_unknown_post_path_returns_404(self, server):
+        status, body = _post(
+            f"http://127.0.0.1:{server.port}/wrong",
+            {"prompt": "hi"},
+        )
+        assert status == 404
+
+    def test_adapter_error_returns_500(self):
+        s = LLMServer(adapter=ErrorLLMAdapter("boom"), port=0)
+        s.start()
+        try:
+            status, body = _post(
+                f"http://127.0.0.1:{s.port}/execute",
+                {"prompt": "hello"},
+            )
+            assert status == 500
+            assert "boom" in body["error"]
+        finally:
+            s.stop()
+
+    def test_config_fields_forwarded(self):
+        """Config fields in request body reach the adapter via RunConfig."""
+        adapter = MockLLMAdapter(mock_response="x")
+        s = LLMServer(adapter=adapter, port=0)
+        s.start()
+        try:
+            status, body = _post(
+                f"http://127.0.0.1:{s.port}/execute",
+                {"prompt": "hi", "config": {"model_name": "gpt-3.5-turbo", "max_tokens": 100}},
+            )
+            assert status == 200
+            assert adapter.last_config.model_name == "gpt-3.5-turbo"
+            assert adapter.last_config.max_tokens == 100
+        finally:
+            s.stop()