fix(review): close doc via try/finally; don't count parse failures as indexed

Address PR #852 review:

- pymupdf.py: the metadata `doc` was only closed on the PdfParseFailed and
  success paths, so a failure in `_extract_metadata`/`mkdir`/`get_settings`
  leaked it. `doc` is only needed for metadata + page_count (the heavy parse
  works from `content` bytes in the worker), so open it, read metadata, and
  close it immediately under try/finally; drop the two later doc.close() calls.

- processor.py: a permanent parse failure early-returned from `_index_document`,
  after which `process_document` still recorded record_qdrant_operation("upsert",
  "success") + record_vector_sync_processing(success) -- counting an OOM/timeout
  bomb as astrolabe_documents_indexed_total{status="success"}. `_index_document`
  now returns False on that path and the caller skips the success metrics (the
  failure is already recorded via document_parse_failed_total + the registry's
  document_parse_total{error}).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/document_processors/pymupdf.py

@@ -107,14 +107,19 @@ class PyMuPDFProcessor(DocumentProcessor):
             if progress_callback:
                 await progress_callback(0, 100, "Opening PDF document")
 
-            # Open document and extract metadata in thread
+            # Open document only to read metadata + page count, then close it
+            # immediately (try/finally so a failure in _extract_metadata can't
+            # leak it). The heavy extraction below works from ``content`` bytes
+            # in the isolated worker, so ``doc`` is not needed past this point.
             doc = await anyio.to_thread.run_sync(  # type: ignore[attr-defined]
                 lambda: pymupdf.open("pdf", content)
             )
-
-            metadata = self._extract_metadata(doc, filename)
-            metadata["file_size"] = len(content)
-            page_count = doc.page_count
+            try:
+                metadata = self._extract_metadata(doc, filename)
+                metadata["file_size"] = len(content)
+                page_count = doc.page_count
+            finally:
+                doc.close()
 
             if progress_callback:
                 await progress_callback(10, 100, f"Extracting {page_count} pages")
@@ -143,7 +148,6 @@ class PyMuPDFProcessor(DocumentProcessor):
                     mem_limit_mb=settings.document_parse_mem_limit_mb,
                 )
             except PdfParseFailed as exc:
-                doc.close()
                 logger.warning(
                     "Isolated PDF parse failed for %s (reason=%s): %s",
                     filename or "<bytes>",
@@ -198,9 +202,6 @@ class PyMuPDFProcessor(DocumentProcessor):
                 metadata["image_paths"] = image_paths
             metadata["page_boundaries"] = page_boundaries
 
-            # Close document
-            doc.close()
-
             if progress_callback:
                 await progress_callback(100, 100, "Processing complete")