refactor(h1): track HEAD keep-alive override as boolean

[trivikr]

This relates to...

HEAD response keep-alive handling in client-h1

Rationale

The HEAD-specific keep-alive override was depending on 1this.connection.toLowerCase()` at headers-complete time. This change replaces that with an explicit tracked boolean so the parser carries only the state needed for the override and avoids string-based re-checks.

Changes

• Track Connection: keep-alive as a boolean on the H1 parser
• Use that boolean in the HEAD keep-alive override path
• Reset the tracked state between responses

Features

N/A

Bug Fixes

N/A

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented
• Review ready
• In review
• Merge ready

Assisted-by: openai:gpt-5.4

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.14%. Comparing base (94c9dea) to head (9f06cd5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5110   +/-   ##
=======================================
  Coverage   93.14%   93.14%           
=======================================
  Files         110      110           
  Lines       35894    35896    +2     
=======================================
+ Hits        33432    33434    +2     
  Misses       2462     2462           

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[mcollina]

lgtm