fix(utils): normalize timm confidences and verify assets

[Borda]

This pull request improves the reliability and correctness of asset downloading and classification confidence handling in the codebase. The main highlights are stricter MD5 verification and retry logic for asset downloads, normalization of classification confidences from timm models, and expanded test coverage for these behaviors.

Asset Download Robustness:

• Refactored the asset download logic to verify MD5 hashes after every fresh download. If a downloaded file fails MD5 verification, it is deleted and the download is retried once before raising an error. This prevents corrupted files from being accepted. (src/supervision/assets/downloader.py, tests/assets/test_downloader.py) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
• Added and updated tests to confirm that corrupted files are detected, retried, and only valid assets are accepted. Tests also ensure MD5 checks are performed on all asset downloads. (tests/assets/test_downloader.py) [1] [2] [3] [4] [5] [6] [7] [8]

Classification Confidence Normalization:

• Changed sv.Classifications.from_timm to apply softmax to model logits before exposing confidence scores, ensuring output is on a normalized probability scale and matches the behavior of from_clip. (src/supervision/classification/core.py, docs/changelog.md) [1] [2]
• Added and improved tests for classification adapters, including checks that softmax is applied and output confidence is normalized. (tests/classification/test_core.py) [1] [2] [3] [4]

Documentation:

• Updated the changelog to document the new asset download verification and classification confidence normalization behaviors. (docs/changelog.md)

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part of #2408

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87%. Comparing base (dde4227) to head (7d386c3).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #2414   +/-   ##
=======================================
  Coverage       87%     87%           
=======================================
  Files           70      70           
  Lines        10227   10240   +13     
=======================================
+ Hits          8853    8868   +15     
+ Misses        1374    1372    -2     

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[Copilot]

Pull request overview

This PR improves correctness and reliability in two core utilities: asset downloading (by verifying MD5 after fresh downloads and retrying once on corruption) and classification adapters (by normalizing timm logits to probabilities via softmax to match CLIP behavior).

Changes:

• Refactor sv.download_assets download flow to MD5-verify newly downloaded payloads and retry once on mismatch.
• Update sv.Classifications.from_timm to softmax logits before exposing confidences.
• Expand tests to cover MD5 verification/retry behavior and timm softmax normalization; document both changes in the changelog.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/supervision/assets/downloader.py	Adds verified download helper(s) and introduces “download → MD5 verify → retry once” behavior for new downloads.
tests/assets/test_downloader.py	Adds/updates unit tests validating MD5 verification on fresh downloads and single-retry behavior on corrupted payloads.
src/supervision/classification/core.py	Normalizes timm confidences via softmax to ensure probability-scale output.
tests/classification/test_core.py	Adds a minimal tensor double softmax + tests for empty-output dtypes and timm softmax normalization.
docs/changelog.md	Documents the MD5 verification/retry change and timm confidence normalization in the Unreleased “Fixed” section.