Adopt mise for development workflows

- Lock Python and uv versions with mise
- Add unified sync, app, test, lint, format, and typecheck tasks
- Update development documentation and strengthen type handling

tests/test_dns.py

@@ -125,6 +125,7 @@ class TestResolveHostname:
             assert resolution.hostname == "slow.example"
             assert resolution.resolved_ip is None
             assert resolution.status == DNSResolutionStatus.RESOLUTION_FAILED
+            assert resolution.error_message is not None
             assert "Timeout after 1.0s" in resolution.error_message
             assert resolution.is_success() is False
 
@@ -256,6 +257,7 @@ class TestResolveHostnamesBatch:
             assert resolutions[0].is_success() is True
             assert resolutions[1].hostname == "error.example"
             assert resolutions[1].is_success() is False
+            assert resolutions[1].error_message is not None
             assert "Network error" in resolutions[1].error_message