Add UMASK environment variable to README

[nitrobass24]

Summary

• Add UMASK to the docker-compose example as a commented-out option
• Add UMASK comment to the docker run example
• Add UMASK row to the environment variables table

The UMASK feature was added in 6fade95 but the README was not updated.

Test plan

• Verify README renders correctly on GitHub

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Added documentation for the optional UMASK environment variable, which controls file permissions with Docker Compose and docker run examples provided.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between b5be932 and 2126a12.

📒 Files selected for processing (1)

• README.md

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📝 Walkthrough

Walkthrough

Documentation updated to introduce the optional UMASK environment variable for controlling file permissions in Docker environments. Added examples showing UMASK usage in Docker Compose and docker run configurations, along with corresponding permission outputs.

Changes

Cohort / File(s)	Summary
Documentation README.md	Added UMASK environment variable documentation with Docker usage examples and permission mapping (002→775/664, 000→777/666).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 Permissions now dance at your command,
With UMASK we grant or withstand,
775 or 777, just take your pick,
Documentation makes configs click! ✨

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch docs/add-umask-to-readme

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}