fix(streams): wait for tcpip client connect instead of retrying

[EmilyRagan]

Summary

TcpipClientStream._connect (Python) spun on a non-blocking socket.connect() and treated EALREADY as success. If the handshake was still pending when the retry ran, the socket got EALREADY and the stream reported connected, even when the connection was later refused.

• On Linux, a refused connection to localhost fails right away. The first retry gets ECONNREFUSED, so CI (ubuntu-latest) passes test_raises_a_timeout_when_unable_to_connect.
• On macOS the refusal arrives later. The retry gets EALREADY first, and the test fails with ConnectionRefusedError not raised.

Fix

Follow the Ruby connect_nonblock flow:

• Call connect_ex. On EINPROGRESS/EWOULDBLOCK, select for writable (plus exceptional, for Windows) with connect_timeout. That parameter was accepted before but never used.
• Read SO_ERROR for the result. A non-zero errno is raised as OSError, which maps to its subclass (for example ConnectionRefusedError).
• If the handshake doesn't finish before the timeout, raise TimeoutError("Connect timeout ...").
• If the socket is closed during connect (ValueError/EBADF/ENOTSOCK), raise RuntimeError("Connect canceled"), as Ruby does.
• The busy loop no longer burns CPU while the handshake is pending.

Tests

New tests in test/streams/test_tcpip_client_stream.py: refused connection on an unused port, a successful connect to a listening server, the timeout path and the canceled path.

On macOS, test/streams and test/interfaces pass (437 tests). Before the fix, test_raises_a_timeout_when_unable_to_connect failed 3 out of 3 runs. It now passes.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.15%. Comparing base (e3a728f) to head (8c84082).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3964      +/-   ##
==========================================
+ Coverage   80.13%   80.15%   +0.02%     
==========================================
  Files         901      901              
  Lines       68370    68374       +4     
  Branches     2699     2699              
==========================================
+ Hits        54789    54808      +19     
+ Misses      12913    12901      -12     
+ Partials      668      665       -3     

Flag	Coverage Δ
frontend	67.05% <ø> (+0.06%)	⬆️
python	80.16% <ø> (+0.03%)	⬆️
ruby-api	82.59% <ø> (ø)
ruby-backend	85.66% <ø> (ø)

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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