feat(domain): add geometry, annotation and sample model

The contract between renderers and exporters. Immutable, pixel-free objects
that can be built, reordered and serialised without touching an image.

- geometry.py: BBox (ordering-normalised, with union/intersection/IoU/clip/
  normalise) and Polygon for rotated or warped regions.
- annotations.py: Page -> Region -> Line -> Word plus Table/TableCell.
  Regions are typed with layout categories used by document-layout
  benchmarks, carry an explicit reading order, and serialise the page back to
  HTML or Markdown - the supervision format document-to-markup models are
  trained against. Tables additionally emit OTSL for table-structure models.
- sample.py: Sample = image + Page + Provenance, where provenance records the
  seed, font, background, renderer, shaper and degradations so any single
  sample can be explained and regenerated.

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

Author: hBouanane

src/ocrsmith/datasets/loaders/HuggingFaceTextLoader.py

@@ -88,9 +88,7 @@ def _check_columns(self, dataset: Any) -> None:
         if not isinstance(columns, (list, tuple)):
             return  # duck-typed source: validated per record instead
         if self.text_column not in columns:
-            raise ValueError(
-                f"Column '{self.text_column}' not found. Available columns: {list(columns)}"
-            )
+            raise ValueError(f"Column '{self.text_column}' not found. Available columns: {list(columns)}")
         if self.title_column and self.title_column not in columns:
             self.title_column = None
 

src/ocrsmith/domain/__init__.py

@@ -0,0 +1,35 @@
+"""Domain model: geometry, annotations and generated samples.
+
+These types are the contract between the renderers that produce pixels and the exporters
+that write datasets. They are immutable and pixel-free, so they can be built, reordered
+and serialised without touching an image.
+"""
+
+from .annotations import (
+    Line,
+    Page,
+    Region,
+    RegionType,
+    Table,
+    TableCell,
+    Word,
+    assign_reading_order,
+)
+from .geometry import BBox, Point, Polygon
+from .sample import Provenance, Sample
+
+__all__ = [
+    "BBox",
+    "Line",
+    "Page",
+    "Point",
+    "Polygon",
+    "Provenance",
+    "Region",
+    "RegionType",
+    "Sample",
+    "Table",
+    "TableCell",
+    "Word",
+    "assign_reading_order",
+]