refactor: solidify startup UX and engine-aware preprocessing

- Slim core deps: move ML stack to optional extras (paddle/tables/figures/scientific/full)
- Lazy settings proxy with config search paths (env var, cwd, user dir)
- New commands: init, demo, setup [basic|full], first-run guard on run/watch
- Engine-aware preprocessing: Paddle gets original image (fixes dark mode 0.83->0.95)
- Results table shows Skipped count; lazy run-dir creation
- kg_ocr marked experimental with extra, Docker defaults with OCR_PIPELINE_CONFIG
- 25/25 tests, ruff clean

src/ocr_pipeline/citations/extractor.py

@@ -13,4 +13,10 @@ from .regex_extractor import (
     format_citations_for_markdown,
 )
 
-__all__ = ["Citation", "GrobidClient", "RegexCitationExtractor", "extract_citations", "format_citations_for_markdown"]
+__all__ = [
+    "Citation",
+    "GrobidClient",
+    "RegexCitationExtractor",
+    "extract_citations",
+    "format_citations_for_markdown",
+]