[michalmaj]

Summary

Add focused Markdown linting with rumdl across local development, pre-commit, and CI.

Why

The repository is documentation-heavy, but its automated checks currently validate links rather than Markdown structure and consistency. rumdl adds a fast linting layer through the existing uv-based workflow without requiring Node.js or reformatting every document.

Changes

• add and configure rumdl as a locked development dependency
• disable only the noisy line-length rule and record two narrow per-file exceptions
• fix the remaining structural issues found by the initial repository audit
• run Markdown linting in pre-commit and the existing Quality checks job
• add a focused chapter and align quickstarts, checklists, troubleshooting, CI logs, and command sequences

Type of change

Select the most relevant option.

• Documentation
• Project configuration
• New feature
• Tests
• CI/CD
• Refactoring
• Bug fix

Checklist

• The change is small and focused
• The pull request title is clear
• I updated documentation if needed
• I added or updated tests if needed
• I ran local checks if applicable

Verification

• uv sync --locked --group dev
• uv run pre-commit validate-config
• uv run pre-commit run --all-files
• uv run ruff check .
• uv run ruff format --check .
• uv run rumdl check .
• uv run pytest --cov=text_toolkit --cov-report=term-missing
• uv run mypy
• uv build --no-sources
• git diff --check

Notes

The existing pytest link check remains responsible for local paths and heading anchors. Human review remains responsible for accuracy, clarity, and teaching quality.