feat(api): author narrator system prompt (voice, [FACT] rule, no-numbers, no player agency)

api/tests/test_prompts.py

@@ -33,3 +33,10 @@ def test_digest_omits_raw_numbers_and_ids():
     assert "40" not in d and "15" not in d      # the deserter dispositions
     assert "brannoc_thane" not in d             # ids stay out; names only
     assert "schema_version" not in d
+
+
+def test_narrator_body_is_authored():
+    body = system_prompt.__wrapped__("narrator")  # bypass lru_cache in case of prior load
+    assert "TBD" not in body
+    assert "[FACT:" in body           # the tag instruction is present
+    assert "second person" in body    # the core task is present