http: fix use-after-free when freeParser is called during llhttp_execute

[Flarna]

When pipelined requests arrive in one TCP segment, llhttp_execute() parses them all in a single call. If a synchronous 'close' event handler invokes freeParser() mid-execution, cleanParser() nulls out parser state while llhttp_execute() is still on the stack, crashing on the next callback.

Add an is_being_freed_ flag that freeParser() sets via parser.markFreed() before cleaning state. Proxy::Raw checks the flag before every callback and returns HPE_USER to abort execution early if set.

Fix/test was created using AI support.

Refs: #61995 (comment)

[nodejs-github-bot]

Review requested:

• @nodejs/http
• @nodejs/net

[codecov]

Codecov Report

❌ Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.65%. Comparing base (afc30b7) to head (d2ea166).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_http_parser.cc	80.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62095      +/-   ##
==========================================
+ Coverage   89.64%   89.65%   +0.01%     
==========================================
  Files         676      676              
  Lines      206326   206338      +12     
  Branches    39528    39524       -4     
==========================================
+ Hits       184960   184996      +36     
+ Misses      13476    13468       -8     
+ Partials     7890     7874      -16     

Files with missing lines	Coverage Δ
lib/_http_common.js	100.00% <100.00%> (ø)
src/node_http_parser.cc	84.68% <80.00%> (-0.05%)	⬇️

... and 31 files with indirect coverage changes

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