feat(dataset): add CreateML format support to DetectionDataset

[madhavcodez]

Description

Adds CreateML object-detection format support to DetectionDataset, with
from_createml() for loading and as_createml() for exporting. supervision
already supports COCO, YOLO, and Pascal VOC; this fills the remaining common
format with a symmetric loader/exporter that mirrors those implementations.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)

Motivation and Context

CreateML is a widely used object-detection annotation format (Apple Create ML,
and one of Roboflow's dataset export options). DetectionDataset can already
round-trip COCO, YOLO, and Pascal VOC, but not CreateML, so users exporting in
that format have to convert manually before loading into supervision. This adds
first-class support following the existing from_<format> / as_<format>
convention.

No existing tracking issue — opening as a feature addition; happy to file one if
the maintainers prefer.

Changes Made

• src/supervision/dataset/formats/createml.py — new module:
  load_createml_annotations, save_createml_annotations, and the helpers
  createml_annotations_to_detections / detections_to_createml_annotations.
  Boxes use CreateML's pixel-space centre + width/height and are converted
  to/from xyxy. Class names are inferred from the labels present in the file
  and assigned sorted, zero-based ids. Image paths are validated against the
  images directory (rejecting .. traversal, absolute paths, the directory
  itself, and directory targets), matching the COCO loader's protection.
• src/supervision/dataset/core.py — DetectionDataset.from_createml() and
  DetectionDataset.as_createml(), plus the format import. Method docstrings
  render automatically in the API docs.
• tests/dataset/formats/test_createml.py — unit tests for the conversion
  helpers, loader, exporter, save→load round-trip (integer and float
  coordinates), global class-id consistency across images, and the path-safety
  guards.

Testing

• I have tested this code locally
• I have added unit tests that prove my feature works
• All new and existing tests pass

Local run: pytest tests/dataset/ passes (including the new test_createml.py),
and ruff check / ruff format --check are clean on the changed files.

[codecov]

Codecov Report

❌ Patch coverage is 86.95652% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 79%. Comparing base (7d22596) to head (0d2ae43).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #2284   +/-   ##
=======================================
  Coverage       79%     79%           
=======================================
  Files           66      67    +1     
  Lines         8569    8638   +69     
=======================================
+ Hits          6806    6866   +60     
- Misses        1763    1772    +9     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.