fix(hono/context): content-type be overridden by default response when append headers

[xx1124961758]

fix node-server bug https://github.com/honojs/node-server/issues/226

• [x] Add tests
• [x] Run tests
• [x] bun run format:fix && bun run lint:fix to format the code
• [ ] Add TSDoc/JSDoc to document the code

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.35%. Comparing base (4eb7979) to head (564a243). Report is 46 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4182      +/-   ##
==========================================
+ Coverage   91.31%   91.35%   +0.03%     
==========================================
  Files         168      168              
  Lines       10790    10707      -83     
  Branches     3067     3088      +21     
==========================================
- Hits         9853     9781      -72     
+ Misses        936      925      -11     
  Partials        1        1              

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[sushichan044]

@xx1124961758 cc: @yusukebe This is just for your information, but it's likely related to this issue as well:

• https://github.com/honojs/hono/issues/3736#issuecomment-2814695601

[yusukebe]

Hi @xx1124961758 Thank you for the PR. I've left the comments.

@sushichan044 Do you think this PR will fix #3736? If so, please review this. You may know the PR #4100 can fix the problem, but I'm not sure we have to merge #4100. So, currently, it's a good idea to use this PR.

[sushichan044]

@yusukebe I also think this pull request can fix the behavior reported in the issue. However, as you said, #4100 is necessary for a fundamental solution. Anyway, I'll review this PR.

[sushichan044]

@xx1124961758 To make things clearer, we should also note in a comment that this fix is an ad-hoc workaround for issue #3736. This conditional branch is special handling, and it's difficult to understand the reasoning behind it without knowing the background.

[yusukebe]

The #4100 was merged. This can be closed. Thank you!