Windows CI: test_legend_comprehensive and test_streamplot runtime failures

[krystophny]

Issue Description

Windows CI tests are failing with runtime errors in test_legend_comprehensive.exe and test_streamplot.exe.

Failing Tests

• test_legend_comprehensive.exe - returns exit code 1
• test_streamplot.exe - returns exit code 1

Impact

These failures are blocking PR merges despite fixes being unrelated to legend/streamplot functionality.

Analysis Needed

• Investigate Windows-specific runtime environment issues
• Check for FFmpeg/external dependency issues on Windows
• Determine if these are consistent failures or flaky tests

Windows CI Log Reference

Run ID: 17219739744
Job ID: 48852051475

This issue is blocking PR #359 which fixes first plot rendering - a completely unrelated component.