fix: each file in a dated session folder becomes its own song

Files directly in YYMMDD/ (e.g. 231015/take1.wav, 231015/take2.wav) all
shared the same nc_folder_path, so take2 was silently merged as a new
version of the take1 song instead of being a separate recording.

Fix: when a file's parent == the session folder, append the file stem
to make a unique virtual nc_folder_path per file. Files in subfolders
(e.g. 231015/groove/take1.wav) are unaffected — they still group by folder.

Applied in both nc_scan.py (manual scan) and internal.py (watcher uploads).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/src/rehearsalhub/routers/internal.py

@@ -13,7 +13,7 @@ from rehearsalhub.repositories.band import BandRepository
 from rehearsalhub.repositories.rehearsal_session import RehearsalSessionRepository
 from rehearsalhub.repositories.song import SongRepository
 from rehearsalhub.schemas.audio_version import AudioVersionCreate
-from rehearsalhub.services.session import parse_rehearsal_date
+from rehearsalhub.services.session import extract_session_folder, parse_rehearsal_date
 from rehearsalhub.services.song import SongService
 
 log = logging.getLogger(__name__)
@@ -72,6 +72,12 @@ async def nc_upload(
     nc_folder = parent.rstrip("/") + "/"
     title = Path(path).stem
 
+    # If the file sits directly inside a dated session folder, give it a unique
+    # virtual folder so it becomes its own song (not merged with other takes).
+    session_folder_path = extract_session_folder(path)
+    if session_folder_path and session_folder_path.rstrip("/") == nc_folder.rstrip("/"):
+        nc_folder = nc_folder + title + "/"
+
     version_repo = AudioVersionRepository(session)
     if event.nc_file_etag and await version_repo.get_by_etag(event.nc_file_etag):
         return {"status": "skipped", "reason": "version already registered"}