Vault format

The app reads and writes an Obsidian vault organised by car, then by workflow: logs, schedule, projects, parts, mods, reference and receipts. Frontmatter dates are YYYY-MM-DD; table dates are MM-DD-YY; approximate mileage stays as written, like 94,xxx.

The full specification is published here with vault export and import in Phase 6. Until then, Appendix A of docs/plan.md is the reference.