feat: scaffold cosma-log-analyzer with 5 deterministic rules + fake MCAP e2e test

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from tests.fixtures.generate_fake_mcap import generate
+
+
+@pytest.fixture(scope="session")
+def fake_mcap(tmp_path_factory: pytest.TempPathFactory) -> Path:
+    path = tmp_path_factory.mktemp("mcap") / "fake.mcap"
+    return generate(path)