fix(docs): render the repository-structure tree as a tree

[hyperpolymath]

The "Repository Structure" block was hard-wrapped by the AsciiDoc→Markdown conversion, so the entire tree collapsed into a single paragraph and rendered as one run-on line.

Rebuilt from the block's own content:

• depth recovered from the │ continuation bars that survived the wrap
• the guide entry moved under .github/, where the guide actually lives
• \# escapes unescaped, └── restored on the last entry of each group
• the block fenced with ```text so it renders as a tree

Every annotation ("Perimeter 1-2" etc.) is preserved — nothing invented, nothing dropped.

[coderabbitai]

📝 Summary

Summary by CodeRabbit

• Documentation
  • Updated the contribution guide with clearer setup instructions and properly formatted section headings.
  • Added reproducible development guidance using Guix.
  • Documented verification commands for checking and testing changes.
  • Expanded repository structure and perimeter classification details.
  • Added branch naming examples and clarified Conventional Commits formatting, including optional bodies and footers.

Walkthrough

The contributor guide now documents Guix-based setup, verification commands, repository structure, contribution headings, branch naming, and Conventional Commits syntax.

Changes

Contributor guide

Layer / File(s)	Summary
Development setup guidance .github/CONTRIBUTING.md	Setup commands are separated. Guix replaces Nix as the recommended environment. Verification commands and a structured repository tree are included.
Contribution and commit guidance .github/CONTRIBUTING.md	Section headings are correctly formatted. Branch naming examples and Conventional Commits guidance now include optional body and footer details.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Suggested reviewers: metadatastician

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly describes a real change: repairing the repository-structure tree rendering in .github/CONTRIBUTING.md.
Description check	✅ Passed	The description accurately explains the documented tree repair and related formatting corrections in .github/CONTRIBUTING.md.

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_{A rabbit checks each command in line
Guix keeps the setup neat and fine
Branch names hop with careful form
Commit notes now weather every storm
The guide grows clear from root to vine}

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