Prepare Jules environment setup scripts

[google-labs-jules]

Added bin/setup to automatically ensure the correct Elixir version (>1.15) is installed and dependencies are compiled. Added bin/ci for running tests and quality checks. Added AGENTS.md to guide future agents on environment setup and project status. Updated .gitignore to ignore local tool installations.

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PR created automatically by Jules for task 18313738655226446864 started by @xiamx

[google-labs-jules]

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