refactor: section the config and make prompts a module

backend/app/domain/matching.py

@@ -12,7 +12,11 @@ _SUFFIX_PATTERN = re.compile(r"(?:\s*(?:\([^)]*\)|\[[^]]*\]))+\s*$")
 
 @dataclass(frozen=True)
 class MatchVerdict:
-    """Explain whether a Spotify track safely matches a proposed candidate."""
+    """Match decision plus the two signals it was derived from.
+
+    A rejection is attributable: either title_similarity fell below the
+    caller's threshold, or is_artist_match is false, or both.
+    """
 
     is_match: bool
     title_similarity: float

backend/app/domain/profile.py

@@ -5,6 +5,9 @@ from app.domain.models import CompressedTasteProfile, TasteProfile, Track
 
 def compress_taste_profile(profile: TasteProfile) -> CompressedTasteProfile:
     """Build compact prompt text and the complete known track identifier set."""
+    # No genre section on purpose: Spotify deprecated the artist genres
+    # field for new apps, so there is no reliable genre source left in the
+    # API. Artist and track names are the genre evidence the model reads.
     sections = (
         _line("Short-term top artists", profile.short_term_artists),
         _line("Long-term top artists", profile.long_term_artists),