feat(community): establish contributor foundation

[codegeist-ai]

Tracking

• Coordinating Issue: Build shared GitHub contributor foundation codegeist#2
• Canonical account task: https://github.com/codegeist-ai/codegeist/blob/feat/contributor-foundation/docs/tasks/T010_build-shared-github-contributor-foundation/task.md

Summary

Establish the devcontainer-kit contributor baseline with 0BSD licensing, fast deterministic pull request CI, repository-specific guidance, and three scoped public-work task specifications. The generated release bundle now carries the license.

Verification

• task check twice, including hostile inherited Git signing/hooks/templates
• Source status and refs unchanged by the fast check
• CI YAML and shell syntax validation
• Exact release manifest and license comparison
• git diff --check

Impact Checklist

• No credentials or private security details are included.
• Documentation and release-contract tests are updated.
• Generated release content will require a maintainer release build after merge.
• Consuming gitlinks are unchanged.
• Contributions are accepted under 0BSD without CLA or DCO.