feat(cli): add structured JSONL session logging for AI output

tests/test_session_log.py

@@ -0,0 +1,22 @@
+"""Tests for structured session logging."""
+
+from __future__ import annotations
+
+import json
+
+from tai.session_log import SessionLogger
+
+
+def test_session_logger_writes_jsonl_row(tmp_path) -> None:  # type: ignore[no-untyped-def]
+    log_path = tmp_path / "logs" / "session.jsonl"
+    logger = SessionLogger.create(str(log_path))
+
+    logger.log_event("analysis_response", {"response": "Root cause is X"})
+
+    lines = log_path.read_text(encoding="utf-8").splitlines()
+    assert len(lines) == 1
+
+    row = json.loads(lines[0])
+    assert row["event"] == "analysis_response"
+    assert row["payload"]["response"] == "Root cause is X"
+    assert "ts" in row