Use package name when __main__.py is used

[yoshibase]

Summary

Fixes #76

Fix

When Fire is invoked from a package's __main__.py via python -m mypackage, help output now shows mypackage instead of __main__.py.

Uses sys.modules['__main__'].__package__ when sys.argv[0] ends with __main__.py.

Tests

cd ../_upstream && python3 -m unittest fire.fire_test.FireTest.testInferCommandNameForMainModule fire.fire_test.FireTest.testInferCommandNameForScript fire.fire_test.FireTest.testFireDefaultName -v

Submit

make submit CONTRIB=contrib-google-python-fire/pr-76-package-name-main

Test plan

• Local tests pass (see README in staging folder)

[google-cla]

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[yoshibase]

Pausing this PR for now: the cla/google check requires signing Google's CLA, and our contributor policy currently excludes repositories that require CLA signing. The fix remains prepared locally and can be resubmitted once CLA signing is feasible. Thank you for understanding.