fix: clarify search cap and batch completion semantics

spotify_client.py

@@ -120,6 +120,7 @@ def list_saved_tracks(limit: int = 50) -> list[dict]:
 
 def search_tracks(query: str, limit: int = 10) -> list[dict]:
     sp = get_client()
+    # Spotify's search endpoint returns at most 50 results per call; no pagination available
     response = sp.search(q=query, type="track", limit=min(limit, 50))
     results = []
     for track in response["tracks"]["items"]:
@@ -156,4 +157,5 @@ def add_tracks_to_playlist(playlist_id: str, track_uris: list[str]) -> dict:
     sp = get_client()
     for i in range(0, len(track_uris), 100):
         sp.playlist_add_items(playlist_id, track_uris[i : i + 100])
+    # Only reached if all batches succeed — any SpotifyException propagates to the caller
     return {"added": len(track_uris)}