Add pre-commit hook to verify static analysis passes & format is correct

[camsim99]

Adds a pre-commit hook that you can install to verify that dart analyze and the package format are correct when you make a call to git commit. Intended to be used when agents are autonomously making & committing changes.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• I signed the CLA.
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• I linked to at least one issue that this PR fixes in the description above.
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[camsim99]

My main worry as of now is that this is sorta slow. For a one char add in a package, it took like 20s. We could potentially cut this down by only formatting Dart files. But I also don't know if it's a huge concern if the main use case here is for agents making sure they are making acceptable commits.

[camsim99]

I also want to add here some tests that integration-ish test that format and analyze are at least in simple cases, doing what we expect.