test: add 106 unit + smoke tests, 93% coverage

- pytest + respx + pytest-cov added as dev dependencies
- tests/smoke/test_registration.py: verify all 66 tools registered and unique
- tests/unit/: 12 files covering every tool — HTTP method, URL, params/body, errors
- tests/config.test.json + conftest.py: zero-network test setup via GITEA_CONFIG
- CLAUDE.md: developer guide with testing philosophy, pyramid, and commands
- server/gitea_mcp.py: get_commit, list_pr_files tools added
- README.md: tool count corrected to 66

tests/unit/test_labels_milestones.py

@@ -0,0 +1,105 @@
+import json
+import pytest
+import httpx
+import respx
+from server.gitea_mcp import (
+    list_labels, create_label, add_issue_labels, list_milestones, create_milestone,
+)
+
+BASE = "https://gitea.test/api/v1"
+
+
+@respx.mock
+def test_list_labels():
+    route = respx.get(f"{BASE}/repos/owner/repo/labels").mock(
+        return_value=httpx.Response(200, json=[{"id": 1, "name": "bug", "color": "#ee0701"}])
+    )
+    result = list_labels("owner", "repo")
+    assert route.called
+    assert result[0]["name"] == "bug"
+
+
+@respx.mock
+def test_create_label():
+    route = respx.post(f"{BASE}/repos/owner/repo/labels").mock(
+        return_value=httpx.Response(201, json={"id": 5, "name": "enhancement"})
+    )
+    result = create_label("owner", "repo", "enhancement", "#84b6eb")
+    assert route.called
+    body = json.loads(route.calls[0].request.content)
+    assert body["name"] == "enhancement"
+    assert body["color"] == "#84b6eb"
+
+
+@respx.mock
+def test_create_label_with_description():
+    route = respx.post(f"{BASE}/repos/owner/repo/labels").mock(
+        return_value=httpx.Response(201, json={"id": 6})
+    )
+    create_label("owner", "repo", "wontfix", "#ffffff", description="Not going to fix")
+    body = json.loads(route.calls[0].request.content)
+    assert body["description"] == "Not going to fix"
+
+
+@respx.mock
+def test_create_label_error():
+    respx.post(f"{BASE}/repos/owner/repo/labels").mock(
+        return_value=httpx.Response(422, json={"message": "validation failed"})
+    )
+    with pytest.raises(RuntimeError, match="422"):
+        create_label("owner", "repo", "bad", "notacolor")
+
+
+@respx.mock
+def test_add_issue_labels():
+    route = respx.post(f"{BASE}/repos/owner/repo/issues/3/labels").mock(
+        return_value=httpx.Response(200, json=[{"id": 1}])
+    )
+    result = add_issue_labels("owner", "repo", 3, [1, 2])
+    assert route.called
+    body = json.loads(route.calls[0].request.content)
+    assert body["labels"] == [1, 2]
+
+
+@respx.mock
+def test_list_milestones():
+    route = respx.get(f"{BASE}/repos/owner/repo/milestones").mock(
+        return_value=httpx.Response(200, json=[{"id": 1, "title": "v1.0"}])
+    )
+    result = list_milestones("owner", "repo")
+    assert route.called
+    assert result[0]["title"] == "v1.0"
+    assert dict(route.calls[0].request.url.params)["state"] == "open"
+
+
+@respx.mock
+def test_list_milestones_closed():
+    route = respx.get(f"{BASE}/repos/owner/repo/milestones").mock(
+        return_value=httpx.Response(200, json=[])
+    )
+    list_milestones("owner", "repo", state="closed")
+    assert dict(route.calls[0].request.url.params)["state"] == "closed"
+
+
+@respx.mock
+def test_create_milestone():
+    route = respx.post(f"{BASE}/repos/owner/repo/milestones").mock(
+        return_value=httpx.Response(201, json={"id": 2, "title": "v2.0"})
+    )
+    result = create_milestone("owner", "repo", "v2.0")
+    assert route.called
+    body = json.loads(route.calls[0].request.content)
+    assert body["title"] == "v2.0"
+    assert "description" not in body
+    assert "due_on" not in body
+
+
+@respx.mock
+def test_create_milestone_with_due_date():
+    route = respx.post(f"{BASE}/repos/owner/repo/milestones").mock(
+        return_value=httpx.Response(201, json={"id": 3})
+    )
+    create_milestone("owner", "repo", "v3.0", description="Major release", due_on="2025-12-31T00:00:00Z")
+    body = json.loads(route.calls[0].request.content)
+    assert body["description"] == "Major release"
+    assert body["due_on"] == "2025-12-31T00:00:00Z"