fix(log): redirect the run log when the first log stream comes back empty

[vdusek]

Python twin of apify/apify-client-js#1105.

call(logger=...) and get_streamed_log() could redirect no log lines at all. When a run hasn't written its first line yet, the API answers GET /logs/:id?stream=1 with an empty 200 and closes it right away. StreamedLog and StreamedLogAsync opened the stream once, so they took that empty response as the whole log.

Both now reopen a stream that ended without any bytes, after a 0.5 s pause. If stop() comes before anything has arrived, the log is read once with get_as_bytes():

• In StreamedLog the streaming thread does that read. stop() cuts the pause short, and a stream that opens while stop() is running is dropped in favor of the read, since it would end after its first chunk.
• In StreamedLogAsync, stop() does the read after cancelling the task, so the task still ends cancelled.

A run that finishes quickly gets its whole log redirected.

Tests cover the same five cases as #1105, for both StreamedLog and StreamedLogAsync and on both HTTP clients:

• the first stream is empty, so the log has to come through the reopened one
• every stream stays empty until stop(), which reads the whole log
• stop() lands while the reopened stream is connecting
• a missing log is neither reopened nor read
• a failing one-shot read is logged and stop() still returns

The first three fail without the fix.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 98.41270% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.38%. Comparing base (ac60559) to head (88b51da).

Files with missing lines	Patch %	Lines
src/apify_client/_streamed_log.py	98.41%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1084      +/-   ##
==========================================
+ Coverage   95.30%   95.38%   +0.07%     
==========================================
  Files          60       60              
  Lines        5755     5788      +33     
==========================================
+ Hits         5485     5521      +36     
+ Misses        270      267       -3     

Flag	Coverage Δ
integration	91.27% <57.14%> (-0.22%)	⬇️
unit	87.97% <98.41%> (+0.22%)	⬆️

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