fix(http1): reset connections for no-body transfer encoding

[mcollina]

Track Transfer-Encoding on HTTP/1.1 responses and avoid reusing a connection after a 204 or 304 response carries it. This extends the existing defensive handling for nonzero Content-Length and prevents trailing bytes from being assigned to a pipelined request.

Adds regression coverage for 204 and 304 responses with both blocking modes.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.52%. Comparing base (c3de472) to head (e208201).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5941   +/-   ##
=======================================
  Coverage   91.52%   91.52%           
=======================================
  Files         113      113           
  Lines       43537    43586   +49     
=======================================
+ Hits        39847    39894   +47     
- Misses       3690     3692    +2     

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