fix: adds steam clean up

[yowainwright]

Discription

Adds stream clean-up in addition to nullish value clean-up.

• update from @fengmk2's identified issue here.
  • feat: fixes mem leak relating to issue-1834 #1893 (comment)
• Stackblitz display issue + fix here.
  • https://stackblitz.com/~/github.com/yowainwright/koa-patch-ISSUE-1834_discussion_r2455395874?file=patch/koa/lib/response.js

Checklist

• I have ensured my pull request is not behind the main or master branch of the original repository.
• I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• I have written a commit message that passes commitlint linting.
• I have ensured that my code changes pass linting tests.
• I have ensured that my code changes pass unit tests.
• I have described my pull request and the reasons for code changes along with context if necessary.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.90%. Comparing base (49a3207) to head (995426e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1910   +/-   ##
=======================================
  Coverage   99.90%   99.90%           
=======================================
  Files           9        9           
  Lines        2074     2081    +7     
=======================================
+ Hits         2072     2079    +7     
  Misses          2        2           

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[Copilot]

Pull Request Overview

This PR addresses a resource leak by ensuring that when a response body stream is replaced with another stream or null value, the original stream is properly destroyed to prevent resource leaks. The fix adds cleanup logic that checks if the original value is a stream and destroys it when it's being replaced, while also preventing unhandled error events during cleanup.

Key Changes:

• Adds stream cleanup logic when a response body stream is replaced
• Includes error handling to prevent unhandled exceptions during stream destruction
• Adds comprehensive test coverage for various stream replacement scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/response.js	Implements stream cleanup logic that destroys the original stream when replaced, with error suppression to prevent unhandled exceptions
tests/response/body.test.js	Adds five test cases covering stream replacement scenarios including cleanup verification and error handling

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[Copilot]

Pull Request Overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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