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/smoke/test_registration.py

@@ -0,0 +1,27 @@
+import asyncio
+from server.gitea_mcp import mcp
+
+EXPECTED_TOOL_COUNT = 66
+
+
+def test_all_tools_registered():
+    tools = asyncio.run(mcp.list_tools())
+    names = sorted(t.name for t in tools)
+    assert len(tools) == EXPECTED_TOOL_COUNT, (
+        f"Expected {EXPECTED_TOOL_COUNT} tools, found {len(tools)}.\n"
+        f"Tools: {names}"
+    )
+
+
+def test_tool_names_unique():
+    tools = asyncio.run(mcp.list_tools())
+    names = [t.name for t in tools]
+    assert len(names) == len(set(names)), (
+        f"Duplicate tool names: {[n for n in names if names.count(n) > 1]}"
+    )
+
+
+def test_all_tools_have_description():
+    tools = asyncio.run(mcp.list_tools())
+    missing = [t.name for t in tools if not t.description]
+    assert not missing, f"Tools without description: {missing}"