[michalmaj]

Summary

Run strict mypy checking in the existing CI job and align every complete workflow example with the new check.

Why

The previous pull request introduced local type checking. CI should now run the same command so type errors cannot be missed when a contributor forgets the local step.

Changes

• add uv run mypy to the existing Quality checks job
• update local check instructions, both quickstarts, the checklist, cheatsheet, CI guide, and troubleshooting material
• add .mypy_cache/ to .gitignore and related examples
• mark the type-checking milestone complete in the roadmap

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

Notes

The job remains named Quality checks. Branch protection still requires that
exact check with strict branch synchronization enabled, so no repository setting
change is needed.

The documentation touches several files because they independently show the
complete local or CI workflow; focused single-tool examples were left alone.

Local checks passed:

• uv run mypy
• uv run ruff check .
• uv run ruff format --check .
• uv run pytest
• uv build --no-sources
• git diff --check