Migrating alpha file import to lean + adding testing

[FergusMunro]

Creates alphaFileImports.lean, replacing alphaFileImports.py. Adjusts workflows and AGENTS.md to use this new script.

Adds alphaFileImports.lean and noAlphaImports.lean to lint_all.lean.

Adds ./Meta/test directory containing a dummy project test_project and a test script testImportScripts.lean that tests alphaFileImports.lean and noAlphaImports.lean fail correctly on the dummy project.

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[jstoobysmith]

This is not quite what I had in mind for the Meta file.
I was thinking e.g. withing the ./PhyslibAlpha project not as a seperate project. Maybe we should save these tests for a future PR, and look at Mathlib to see what they do here.

[FergusMunro]

I wasn't too happy with it either. I've temporarily removed it and when I get the chance I'll try to look at Mathlib.

[jstoobysmith]

awaiting-author

[jstoobysmith]

Maybe would be nice to remove these new lines from within definitions.

[FergusMunro]

I've removed the newlines, if there's some other style changes you'd like to make let me know.

[jstoobysmith]

For meta programming I think it is a bit more loose than the Lean code itself. But the main ones are this, definitions should be written like checkAllFilesImported not like check_all_files_imported, and generally make things concise and readable where possible.

[jstoobysmith]

Approved - looks good. Thanks