Structure refactor workflow

1. Inspect the current layout with tree -h src (or tree -h <specified_dir>) and read the main entry points and largest nearby files.
2. Reorganize by responsibility to improve cohesion and reduce coupling: split oversized files, group related modules, and add directories only when they make ownership clearer.
3. Update imports as you go and preserve existing behavior unless broader changes are explicitly requested.
4. Run the lightest relevant verification, such as typecheck or lint, to catch broken imports or module wiring.
5. Commit and push the changes, then run either the open-pr or update-pr skill.
6. Summarize what moved and why the new structure is easier to maintain.