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_branches.py

@@ -0,0 +1,89 @@
+import json
+import pytest
+import httpx
+import respx
+from server.gitea_mcp import list_branches, get_branch, create_branch, delete_branch, list_tags
+
+BASE = "https://gitea.test/api/v1"
+
+
+@respx.mock
+def test_list_branches():
+    route = respx.get(f"{BASE}/repos/owner/repo/branches").mock(
+        return_value=httpx.Response(200, json=[{"name": "main"}])
+    )
+    result = list_branches("owner", "repo")
+    assert route.called
+    assert result[0]["name"] == "main"
+    assert dict(route.calls[0].request.url.params)["limit"] == "50"
+
+
+@respx.mock
+def test_get_branch():
+    route = respx.get(f"{BASE}/repos/owner/repo/branches/main").mock(
+        return_value=httpx.Response(200, json={"name": "main"})
+    )
+    result = get_branch("owner", "repo", "main")
+    assert route.called
+    assert result["name"] == "main"
+
+
+@respx.mock
+def test_get_branch_with_slash_in_name():
+    route = respx.get(f"{BASE}/repos/owner/repo/branches/feature%2Ffoo").mock(
+        return_value=httpx.Response(200, json={"name": "feature/foo"})
+    )
+    result = get_branch("owner", "repo", "feature/foo")
+    assert route.called
+
+
+@respx.mock
+def test_get_branch_not_found():
+    respx.get(f"{BASE}/repos/owner/repo/branches/missing").mock(
+        return_value=httpx.Response(404, json={"message": "not found"})
+    )
+    with pytest.raises(RuntimeError, match="404"):
+        get_branch("owner", "repo", "missing")
+
+
+@respx.mock
+def test_create_branch():
+    route = respx.post(f"{BASE}/repos/owner/repo/branches").mock(
+        return_value=httpx.Response(201, json={"name": "feature/new"})
+    )
+    result = create_branch("owner", "repo", "feature/new")
+    assert route.called
+    body = json.loads(route.calls[0].request.content)
+    assert body["new_branch_name"] == "feature/new"
+    assert "old_branch_name" not in body
+
+
+@respx.mock
+def test_create_branch_from_specific():
+    route = respx.post(f"{BASE}/repos/owner/repo/branches").mock(
+        return_value=httpx.Response(201, json={"name": "hotfix"})
+    )
+    create_branch("owner", "repo", "hotfix", old_branch_name="main")
+    body = json.loads(route.calls[0].request.content)
+    assert body["old_branch_name"] == "main"
+
+
+@respx.mock
+def test_delete_branch():
+    route = respx.delete(f"{BASE}/repos/owner/repo/branches/old-branch").mock(
+        return_value=httpx.Response(204)
+    )
+    result = delete_branch("owner", "repo", "old-branch")
+    assert route.called
+    assert result == {"success": True}
+
+
+@respx.mock
+def test_list_tags():
+    route = respx.get(f"{BASE}/repos/owner/repo/tags").mock(
+        return_value=httpx.Response(200, json=[{"name": "v1.0.0"}])
+    )
+    result = list_tags("owner", "repo")
+    assert route.called
+    assert result[0]["name"] == "v1.0.0"
+    assert dict(route.calls[0].request.url.params)["limit"] == "20"