test: fix flaky test_crawler_intermediate_statistics on Windows

[vdusek]

test_crawler_intermediate_statistics failed on Windows 3.12 (run) with 98582 µs >= 100000 µs. The test sleeps 100 ms with asyncio.sleep and expects crawler_runtime to be at least that long, but crawler_runtime comes from datetime.now(). On Windows before Python 3.13 that clock ticks every ~15.6 ms, and the only slack in the test was the poll lag, which can be close to zero.

The test now takes its own datetime.now() readings when it sees the crawler start and after the sleep, and asserts the runtime is at least the gap between them. Both sides use the same clock, and the check still fails if the runtime isn't updated while the crawler runs.

✍️ Drafted by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.84%. Comparing base (c69f75f) to head (d9dc0d0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2265      +/-   ##
==========================================
- Coverage   93.88%   93.84%   -0.05%     
==========================================
  Files         182      182              
  Lines       13140    13140              
==========================================
- Hits        12337    12331       -6     
- Misses        803      809       +6     

Flag	Coverage Δ
unit	93.84% <ø> (-0.05%)	⬇️

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