feat(journal): closeout system prompt with structured-field guard

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

tests/test_journal_closeout.py

@@ -51,3 +51,14 @@ def test_build_transcript_keeps_only_last_20_messages():
     # Newest 20 means msg-10 through msg-29
     assert lines[0] == "USER: msg-10"
     assert lines[-1] == "USER: msg-29"
+
+
+def test_system_prompt_lists_structured_fields_to_exclude():
+    """The prompt must explicitly tell the LLM not to restate structured
+    fields, so the freeform learned_summary stays a narrow lane."""
+    from fabledassistant.services.journal_closeout import SYSTEM_PROMPT
+
+    text = SYSTEM_PROMPT.lower()
+    for field in ("name", "job title", "industry", "expertise", "response style", "tone", "interests"):
+        assert field in text, f"system prompt should mention '{field}'"
+    assert "(nothing to note)" in SYSTEM_PROMPT