Add justfile, ols/odinfmt config, tests and Gitea workflows; drop odin.json

- justfile with build/run/check/test/release/package/fmt/clean recipes
- ols.json and odinfmt.json for neovim (ols)
- Tests for memory game rules and card animation; memory.deal and
  memory.select_card split out so logic is testable without a window
- Gitea workflows: build+test on main/develop, package and upload to the
  generic package registry on version branches
- Game changes to the executable's directory so packaged builds find assets

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,3 +1,30 @@
 # HanjaKanaMun
 
-Odin + raylib multilingual application (Thai, Korean, Japanese)
+Odin + raylib memory card game for learning Japanese, Korean and Thai scripts.
+
+## Development
+
+Requires [Odin](https://odin-lang.org) (dev-2026-09) and [just](https://just.systems).
+
+```sh
+just run              # build and play (debug)
+just check            # type-check with -vet
+just test             # run tests
+just package 1.0      # release build -> build/HanjaKanaMun_1.0_<os>_<arch>.tar.gz
+```
+
+### Neovim
+
+`ols.json` and `odinfmt.json` configure the [ols](https://github.com/DanielGavin/ols) language server and formatter.
+Install ols (e.g. `:MasonInstall ols`) and enable it with nvim-lspconfig: `vim.lsp.enable('ols')`.
+Formatting goes through ols (`vim.lsp.buf.format()`), or `just fmt` if `odinfmt` is on your PATH.
+
+## CI
+
+- `.gitea/workflows/gitea-build.yaml`: check, test and build on pushes and PRs to `main` and `develop`.
+- `.gitea/workflows/gitea-release.yaml`: on version branches like `1.0`, packages the Linux build and uploads it to
+  the Gitea generic package registry (`HanjaKanaMun/<version>`). Needs a `TOKEN` secret with package write access.
+
+## Credits
+
+Font: M PLUS Rounded 1c, SIL Open Font License (`assets/MPLUSRounded1c-OFL.txt`).