fix(http): handle HEAD requests in serveDir

[wilkmaciej]

Summary

• serveDir() now accepts HEAD requests alongside GET, resolving the inconsistency where serveFile() already supported HEAD but serveDir() returned 405
• serveDirIndex() returns a bodiless response with correct Content-Length for HEAD requests on directory listings

Closes #6750
Supersedes #6752

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.02%. Comparing base (4221795) to head (bd97d53).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7024      +/-   ##
==========================================
+ Coverage   93.73%   94.02%   +0.28%     
==========================================
  Files         620      627       +7     
  Lines       49388    50034     +646     
  Branches     8651     8809     +158     
==========================================
+ Hits        46293    47042     +749     
+ Misses       3025     2413     -612     
- Partials       70      579     +509     

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[kt3k]

LGTM. Nice! Thanks

retract

[kt3k]

Thanks for the PR. Left one comment

[kt3k]

LGTM