fix(library): normalize MIME types to file extensions in Daedalus ingest

Daedalus may send `file_type` as a MIME type (e.g. `text/markdown`) rather
than a bare extension. Add a `_normalize_file_type` helper with a MIME→ext
lookup table and sensible fallbacks so ingested items are stored with
proper extensions like `md` instead of `text/markdown`.

mnemosyne/library/tasks.py

@@ -17,6 +17,41 @@ logger = logging.getLogger(__name__)
 # Cache key pattern for task progress
 PROGRESS_KEY = "library:task:{task_id}:progress"
 
+# MIME type → file extension, for when Daedalus sends content_type as file_type
+_MIME_TO_EXT = {
+    "text/markdown": "md",
+    "text/plain": "txt",
+    "text/html": "html",
+    "text/csv": "csv",
+    "text/xml": "xml",
+    "application/pdf": "pdf",
+    "application/epub+zip": "epub",
+    "application/vnd.openxmlformats-officedocument.wordprocessingml.document": "docx",
+    "application/vnd.openxmlformats-officedocument.presentationml.presentation": "pptx",
+    "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet": "xlsx",
+    "application/json": "json",
+    "image/jpeg": "jpg",
+    "image/png": "png",
+    "image/gif": "gif",
+    "image/webp": "webp",
+    "image/tiff": "tiff",
+}
+
+
+def _normalize_file_type(raw: str) -> str:
+    """Convert a MIME type or extension string to a bare extension."""
+    raw = (raw or "").strip().lower()
+    if "/" in raw:
+        # It's a MIME type — look up or derive from the subtype
+        ext = _MIME_TO_EXT.get(raw)
+        if ext:
+            return ext
+        # Fallback: use the part after the slash, strip vendor prefixes
+        subtype = raw.split("/", 1)[1]
+        subtype = subtype.split("+")[-1]  # e.g. "epub+zip" → "zip"; "vnd.ms-excel" → keep
+        return subtype.lstrip(".") or "bin"
+    return raw.lstrip(".") or "bin"
+
 
 def _update_progress(task, percent: int, message: str):
     """
@@ -373,7 +408,7 @@ def ingest_from_daedalus(self, job_id: str):
         data = fetch_from_daedalus(job.s3_key)
 
         # --- 4. Create Item node ---
-        ext = (job.file_type or "bin").lstrip(".").lower() or "bin"
+        ext = _normalize_file_type(job.file_type)
         item = Item(
             title=job.title,
             file_type=ext,