gallery_service._provenance_clause artist branch was correlating its bare
Post reference to the outer query's primary_post_id outer-join, so the
artist filter silently matched zero rows for images with no primary post.
Alias Post inside the EXISTS subquery so SQLAlchemy adds it to the inner
FROM rather than treating it as a correlated outer table.
Five sidecar/import tests still asserted that a synthetic Source row
appears after a filesystem import. Alembic 0030 retired that behavior;
the Post sits null-source and the artist linkage lives on Post.artist_id.
Updated test_sidecar_creates_provenance, test_reimport_same_post_idempotent,
test_sidecar_artist_used_when_no_folder_artist, test_supersede_applies_new_file_sidecar,
and test_apply_sidecar_recovers_from_integrity_error to assert
post.source_id IS NULL + post.artist_id linkage instead.
_apply_sidecar is additive: it find-or-creates Post/Source/ImageProvenance
and sets primary_post_id NULL-only, so any IR-migration provenance on the
existing row survives untouched and the new GS sidecar adds a second
ImageProvenance pointing at the freshly-created Post.
Wrapped in try/except so a malformed sidecar can't unwind the file-swap
commit — the file replacement is the critical operation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen