chore: postpone annotations in src typing

[Borda]

Add postponed annotation evaluation to remaining source modules that already use modern annotation syntax.

Keep the change limited to typing syntax cleanup for Python 3.10 compatibility.

Part of #2260

[codecov]

Codecov Report

❌ Patch coverage is 81.69014% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 82%. Comparing base (4b867f2) to head (8f88530).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #2356   +/-   ##
=======================================
- Coverage       82%     82%   -0%     
=======================================
  Files           68      68           
  Lines         9507    9523   +16     
=======================================
+ Hits          7811    7823   +12     
- Misses        1696    1700    +4     

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[Copilot]

Pull request overview

This PR standardizes typing syntax across remaining modules as part of the Python 3.10 baseline work (referenced by #2260), primarily by enabling postponed annotation evaluation and migrating legacy typing constructs (e.g., Optional/Union) to modern syntax.

Changes:

• Added from __future__ import annotations to additional modules to postpone annotation evaluation consistently.
• Replaced Optional[...] / Union[...] usage with T | None / A | B where applicable.
• Added # type: ignore[import-untyped] on deprecate imports to keep type checking clean.

Assessment (n/5):

• Code quality: 3/5
• Testing: 3/5
• Documentation: 3/5

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/supervision/validators/init.py	Add postponed annotations and modernize optional dict typing; mark deprecate as untyped import.
src/supervision/utils/iterables.py	Add postponed annotation evaluation import.
src/supervision/utils/image.py	Mark deprecate import as untyped.
src/supervision/utils/conversion.py	Add postponed annotations and mark deprecate import as untyped.
src/supervision/tracker/byte_tracker/core.py	Mark deprecate import as untyped.
src/supervision/metrics/detection.py	Reformat deprecate imports and mark as untyped.
src/supervision/key_points/skeletons.py	Add postponed annotation evaluation import.
src/supervision/key_points/core.py	Replace Union[...] aliases with `
src/supervision/geometry/utils.py	Add postponed annotation evaluation import.
src/supervision/draw/base.py	Add postponed annotation evaluation import.
src/supervision/detection/utils/internal.py	Replace Union[...] in cast with `
src/supervision/detection/utils/boxes.py	Mark deprecate import as untyped.
src/supervision/detection/tools/inference_slicer.py	Switch TypeGuard import to stdlib typing (Py3.10+) and simplify typing imports.
src/supervision/dataset/utils.py	Mark deprecate import as untyped.
src/supervision/dataset/formats/coco.py	Add postponed annotations; replace Union[...] with `
src/supervision/assets/list.py	Add postponed annotations and use unquoted Assets return annotation.
src/supervision/annotators/core.py	Refactor _load_icon typing around letterbox_image call.