Add canned gear and prompt smoke-test commands

[GoatInAHat]

Summary

• add a canned SGEARTEST10 command that builds a 10-tooth gear with hard-coded parameters for non-interactive smoke checks
• add a minimal SGEARLINE command that prompts for a length and draws a line to validate user input flow
• verify both commands via new static tests in the loader test suite

Testing

• ./tests/auto_load_test.sh

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Codex Task