Ensure close and connection_lost do not race in Win32

[puddly]

The earlier fix we made for POSIX was also required for Win32. I've added a slow close test to catch more errors like this in the future, in addition to running the lifecycle test suite twice: once with eager task execution, once without.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.15%. Comparing base (fb3ef82) to head (4b21dd2).

Files with missing lines	Patch %	Lines
serialx/platforms/serial_win32.py	75.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #101      +/-   ##
==========================================
- Coverage   92.20%   92.15%   -0.05%     
==========================================
  Files          22       22              
  Lines        3654     3660       +6     
==========================================
+ Hits         3369     3373       +4     
- Misses        285      287       +2     

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[Copilot]

Pull request overview

Aligns the Win32 async transport close lifecycle with the POSIX behavior by ensuring handle-release work completes before protocol.connection_lost() is dispatched, and strengthens lifecycle regression coverage by running the suite under both lazy and eager task execution.

Changes:

• Win32: defer connection_lost dispatch until after the underlying handle-close completes, stashing the loss reason meanwhile.
• Tests: run async lifecycle tests twice (default vs eager task factory) and add a “slow close” regression test to assert connection_lost does not fire before the releasing syscall returns.

Reviewed changes

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

File	Description
tests/test_async_lifecycle.py	Adds eager-task parametrization and a slow-close lifecycle regression test.
serialx/platforms/serial_win32.py	Reorders Win32 close/loss signaling to avoid races between closing and connection_lost.

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