fix: robust NC activity filter, title extraction, scan result detail

Watcher:
- Accept both NC 22+ (type="file_created") and older NC (subject="created_self")
  so the upload filter works across all Nextcloud versions
- Add .opus to audio_extensions
- Fix tests: set nc.username on mocks, use realistic activity dicts with type field
- Add tests for old NC style, non-band path filter, normalize_nc_path, cursor advance

API:
- Fix internal.py title extraction: always use filename stem (was using
  parts[-2] for >3-part paths, which gave folder name instead of song title)
- nc-scan now returns NcScanResult with folder, files_found, imported, skipped counts
  instead of bare song list — gives the UI actionable feedback

Web:
- Show rich scan result message: folder scanned, count imported, count already registered

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

api/src/rehearsalhub/routers/internal.py

@@ -53,12 +53,17 @@ async def nc_upload(
         log.warning("nc-upload: band slug '%s' not found in DB", band_slug)
         return {"status": "skipped", "reason": "band not found"}
 
-    # Determine song title and folder from remaining path segments
-    # e.g. bands/my-band/songs/session1/rec.mp3 → folder=bands/my-band/songs/session1/, title=session1
-    # e.g. bands/my-band/rec.mp3 → folder=bands/my-band/, title=rec
+    # Determine song title and folder from path.
+    # The title is always the filename stem (e.g. "take1" from "take1.wav").
+    # The nc_folder groups all versions of the same recording (the parent directory).
+    #
+    # Examples:
+    #   bands/my-band/take1.wav            → folder=bands/my-band/,         title=take1
+    #   bands/my-band/231015/take1.wav     → folder=bands/my-band/231015/,   title=take1
+    #   bands/my-band/songs/groove/take1.wav → folder=bands/my-band/songs/groove/, title=take1
     parent = str(Path(path).parent)
     nc_folder = parent.rstrip("/") + "/"
-    title = Path(path).stem if len(parts) == 3 else parts[-2]
+    title = Path(path).stem
 
     version_repo = AudioVersionRepository(session)
     if event.nc_file_etag and await version_repo.get_by_etag(event.nc_file_etag):

api/src/rehearsalhub/routers/songs.py

@@ -3,6 +3,7 @@ import uuid
 from pathlib import Path
 
 from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from rehearsalhub.db.engine import get_session
@@ -25,6 +26,14 @@ router = APIRouter(tags=["songs"])
 AUDIO_EXTENSIONS = {".mp3", ".wav", ".flac", ".ogg", ".m4a", ".aac", ".opus"}
 
 
+class NcScanResult(BaseModel):
+    folder: str
+    files_found: int
+    imported: int
+    skipped: int
+    songs: list[SongRead]
+
+
 @router.get("/bands/{band_id}/songs", response_model=list[SongRead])
 async def list_songs(
     band_id: uuid.UUID,
@@ -65,7 +74,7 @@ async def create_song(
     return read
 
 
-@router.post("/bands/{band_id}/nc-scan", response_model=list[SongRead])
+@router.post("/bands/{band_id}/nc-scan", response_model=NcScanResult)
 async def scan_nextcloud(
     band_id: uuid.UUID,
     session: AsyncSession = Depends(get_session),
@@ -98,7 +107,8 @@ async def scan_nextcloud(
             return href[len(dav_prefix):]
         return href.lstrip("/")
 
-    imported: list[SongRead] = []
+    imported_songs: list[SongRead] = []
+    skipped_count = 0
     band_folder = band.nc_folder_path or f"bands/{band.slug}/"
 
     log.info("Starting NC scan for band '%s' in folder '%s'", band.slug, band_folder)
@@ -159,6 +169,7 @@ async def scan_nextcloud(
 
         if etag and await version_repo.get_by_etag(etag):
             log.debug("Skipping '%s' — etag already registered", nc_file_path)
+            skipped_count += 1
             continue
 
         # Find or create song record
@@ -191,12 +202,21 @@ async def scan_nextcloud(
 
         read = SongRead.model_validate(song)
         read.version_count = 1
-        imported.append(read)
+        imported_songs.append(read)
         label_info = f" [rehearsal: {rehearsal_label}]" if rehearsal_label else ""
         log.info("Imported '%s' as song '%s'%s", nc_file_path, song_title, label_info)
 
-    log.info("NC scan complete: %d new versions imported", len(imported))
-    return imported
+    log.info(
+        "NC scan complete for '%s': %d imported, %d skipped (already registered)",
+        band_folder, len(imported_songs), skipped_count,
+    )
+    return NcScanResult(
+        folder=band_folder,
+        files_found=len(to_import),
+        imported=len(imported_songs),
+        skipped=skipped_count,
+        songs=imported_songs,
+    )
 
 
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