More consistent newline behavior

[trask]

This seemed like a good change independently, but also builds towards the fix in #511

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.0%. Comparing base (c5c66ba) to head (609f13c).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/weaver_forge/src/formats/html.rs	88.8%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #509   +/-   ##
=====================================
  Coverage   73.9%   74.0%           
=====================================
  Files         50      50           
  Lines       3911    3916    +5     
=====================================
+ Hits        2894    2899    +5     
  Misses      1017    1017           

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