create_document_from_source resolves a fetcher per call and never closed
it, so every one-shot URL or WebDAV ingest leaked an httpx connection
pool. Close it, but only when we built it: resolve_adhoc_fetcher returns
a caller-supplied source when one matches the URI, and the ingester keeps
those open across jobs.
Directory ingestion also yielded symlinked files resolving outside the
directory it was given. rglob does not recurse into symlinked
directories, so a symlinked file was the only way out of the tree; skip
those, as FSSource.discover already does.
The chunk repository docstring named client._ensure_chunks_embedded,
which does not exist.
