test: let the restarted silent-stream log end before stopping it

[vdusek]

test_streamed_log_sync_stop_returns_on_silent_stream restarts the log and calls stop() right away. When stop() lands before the restarted stream delivers its line, the thread falls back to reading the whole log, which the test doesn't serve. The 500 then goes through the client's retry backoff for longer than the 5 s join, and the final Log redirection stopped due to unexpected error record shows up in the caplog of a later test on the same xdist worker (failed run).

The test now waits for the restarted thread to finish on its own (the released server ends the stream after one line), asserts that it did, and only then calls stop(). Running the two tests back to back failed 12/12 before the change and passes after it.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.50%. Comparing base (a370e7a) to head (055e568).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1112      +/-   ##
==========================================
- Coverage   95.53%   95.50%   -0.04%     
==========================================
  Files          61       61              
  Lines        5935     5935              
==========================================
- Hits         5670     5668       -2     
- Misses        265      267       +2     

Flag	Coverage Δ
integration	90.85% <ø> (+0.26%)	⬆️
unit	88.91% <ø> (-0.04%)	⬇️

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[Mantisus]

LGTM

[apify-approval-mirror]

Mirroring approval from @Mantisus.