fix(ci): restore green backend gate after engine pin

Ruff: declare adapter re-exports via __all__ in docling_extractor
(F401) and sort the engine import block in the adapter test (I001).
Pytest: engine-dependent tests now importorskip the pinned engine —
CI installs light deps only and the engine repo is private, so they
skip visibly there and run in Docker/dev envs with the engine.

Verified: ruff clean; pytest 74 passed + 2 skipped without engine,
80 passed with the pinned engine v0.1.0 installed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/ingestion/docling_extractor.py

@@ -15,6 +15,17 @@ from teamhub_document_recognition_engine import extract as _engine_extract
 
 from app.config import settings
 
+# Re-exported engine models: chunker, table/figure processors and tests import
+# them from this adapter instead of depending on the engine package directly.
+__all__ = [
+    "ExtractedBlock",
+    "ExtractedFigure",
+    "ExtractedPage",
+    "ExtractedTable",
+    "ExtractionResult",
+    "extract",
+]
+
 
 def extract(pdf_path: Path) -> ExtractionResult:
     return _engine_extract(pdf_path, docling_ocr_enabled=settings.docling_ocr_enabled)