docs: add usage, acceptance checklist and build workflow

README.md

@@ -1,5 +1,14 @@
 # YKanBan
 
-My personal used local/offline kanban.
+A personal, local/offline kanban board. Cross-platform desktop app built with Avalonia UI and MVVM. Each workspace stores its data in a `.ykanban` folder at the project root, Git-style.
 
-WIP.
+See [USAGE.md](USAGE.md) for workspaces, backups, the search syntax and command-line usage.
+
+## Build and test
+
+```
+dotnet build YKanBan.slnx
+dotnet test YKanBan.slnx
+```
+
+Packages are pinned in `YKanBan/YKanBan.csproj`.