fix(static): support HEAD without opening files

[paulkagiri]

Summary of Changes

Static routes now handle HEAD separately from GET: they compute the same response metadata without opening a file stream, preserve range headers for ranged HEAD requests, and return 405 Method Not Allowed for unsupported methods. OPTIONS now advertises both GET and HEAD.

Related Issues

Closes #2337

Pull Request Checklist

• Applied changes to both WSGI and ASGI code paths and interfaces (where applicable).
• Added tests for changed code.
• Performed automated tests and code quality checks by running tox.
• Prefixed code comments with GitHub nick and an appropriate prefix.
• Coding style is consistent with the rest of the framework.
• Updated documentation for changed code.
• Changes have towncrier news fragments under docs/_newsfragments/, with the file name format {issue_number}.{fragment_type}.rst.
• LLM output, if any, has been carefully reviewed and tested by a human developer.

Testing performed:

• python -m pytest tests/test_static.py -q
• git diff --check

[vytas7]

Hey, and thanks for this PR.
Please check the failing CI, most of the gates fail on your changes.

[vytas7]

Hi again @paulkagiri, have you have a chance to review the CI failures?

[paulkagiri]

Addressed the CI failures from the review.

Changes made:

• Extracted static file lookup into a helper to bring StaticRoute.__call__ back under the Ruff complexity threshold.
• Fixed the long test line flagged by Ruff.
• Updated the CORS static-route OPTIONS expectation now that static routes advertise both GET and HEAD.

Validation:

• python -m tox -e pep8
• python -m tox -e ruff
• python -m tox -e mintest
• git diff --check

[codecov]

Codecov Report

❌ Patch coverage is 82.75862% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.87%. Comparing base (eddfeb4) to head (63f3ca0).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
falcon/routing/static.py	82.75%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #2645      +/-   ##
===========================================
- Coverage   100.00%   99.87%   -0.13%     
===========================================
  Files           64       64              
  Lines         7976     8010      +34     
  Branches      1102     1109       +7     
===========================================
+ Hits          7976     8000      +24     
- Misses           0        8       +8     
- Partials         0        2       +2     

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[vytas7]

Can you please run tox without any parameters (i.e., with the default environments) on your side to verify before pushing?
(It should be easy regardless whether you are a human or AI.)