No close_notify from the finalizer

[krynju]

Split out of #73, as asked in the review there: an independent fix, against main.

Bug. The finalizer calls close(ssl), which sends the close_notify, a socket write. A write that has to wait for the socket switches tasks, which a finalizer may not do. On nightly, where the socket write path waits more readily, NoCloseStream printed "task switch not allowed from inside gc finalizer"; on released Julia it only waits when the socket buffer is full, so the hazard is latent.

Fix. The finalizer calls close(ssl, false): the SSL object is freed and the socket closed, nothing is written. A stream the user wants shut down cleanly still gets its close_notify from an explicit close(ssl).

No test: NoCloseStream is the existing coverage, and the failure depends on GC timing. No version bump; the fixes can be released together.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.39%. Comparing base (10f7b7b) to head (149701f).
⚠️ Report is 41 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   77.56%   77.39%   -0.17%     
==========================================
  Files           2        2              
  Lines        1083     1190     +107     
==========================================
+ Hits          840      921      +81     
- Misses        243      269      +26     

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