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>

.github/workflows/ci.yml

@@ -40,10 +40,13 @@ jobs:
         run: python -m compileall -q app scripts tests
 
       - name: Pytest (unit only — heavy deps excluded)
+        # test_chunker.py skips here: it needs the pinned document recognition
+        # engine (private TeamHUB_Engines repo, no PAT secret configured).
+        # It runs in the Docker image and in dev envs with the engine installed.
         run: |
           pytest tests/test_hashing.py tests/test_quality.py \
                  tests/test_chunker.py tests/test_duplicates.py \
-                 tests/test_hybrid_search.py -q
+                 tests/test_hybrid_search.py -q -rs
 
       - name: docker compose config
         run: docker compose config --quiet