fix(tokens): normalize inverted bbox in get_location instead of asserting

[maxtaran2010]

Fixes #620

Problem

`DocumentToken.get_location()` in `docling_core/types/doc/tokens.py` asserted `bbox[0] <= bbox[2]` and `bbox[1] <= bbox[3]`. Near-degenerate elements (e.g. a thin decorative rule whose layout-model regression produces a slightly inverted bbox) can violate this by a fraction of a point, which crashes `export_to_doctags(add_location=True)`:

File ".../docling_core/types/doc/tokens.py", line 307, in get_location
    assert bbox[1] <= bbox[3], f"bbox[1]<=bbox[3] => {bbox[1]}<={bbox[3]}"
AssertionError: bbox[1]<=bbox[3] => 633.3925132751465<=625.6789665222168

The asserts were redundant: the method already emits correctly-ordered location tokens via `min()`/`max()` downstream. The probability of hitting one such element grows with page count, so long documents are the most affected.

Fix

Sort the coordinates before normalization (mirroring the existing `min()`/`max()` behaviour) and drop the asserts. Output is unchanged for well-formed boxes and now correct instead of crashing for inverted ones.

Tests

Added `test/test_tokens.py` covering:

• a normal bbox (exact token output)
• the partially inverted bbox from the issue repro
• a fully inverted bbox

All pass; existing `test_serialization_doctag.py` and `test_doctags_load.py` (17 tests) still pass, and `ruff` is clean.

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[Copilot]

Pull request overview

This PR updates DocumentToken.get_location() to handle slightly inverted bounding boxes by normalizing coordinate order instead of asserting, preventing crashes during DocTags export for near-degenerate layout elements (Issue #620).

Changes:

• Normalize potentially inverted bbox coordinates using sorted() and remove the crash-causing assertions.
• Add unit tests covering normal, partially inverted (issue repro), and fully inverted bounding boxes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
docling_core/types/doc/tokens.py	Normalizes inverted bbox coordinates before computing location tokens, avoiding asserts/crashes.
test/test_tokens.py	Adds regression/unit tests to ensure inverted bboxes serialize consistently and don’t crash.

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[ceberam]

Thanks @maxtaran2010 for this contribution. The fix is correct and the change itself is clean and minimal.

A couple of comments:

• However, after the sort, left <= right and top <= bottom is guaranteed, so dividing by positive page dimensions preserves that: x0 <= x1 and y0 <= y1. The four calls on lines 320–323 can now be written without min() or max(). Could you please simplify those lines?
• The inline comment on get_location is very informative for users to understand the eventual normalization. Could you please add the comment to the function docstring instead of the inline comments?