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>

AGENTS.md

@@ -3,7 +3,7 @@
 ## Overview
 Odin + raylib multilingual memory card game for learning Japanese (Hiragana/Katakana), Korean (Hangul), and Thai scripts.
 
-Build and run: `odin run .` (check with `odin check . -vet`)
+Commands (see `justfile`): `just run`, `just check`, `just test`, `just package <version>`
 
 ## Current Status
 
@@ -32,14 +32,20 @@ Build and run: `odin run .` (check with `odin check . -vet`)
 1. **Font glyphs must be listed**: raylib only bakes the codepoints passed to `LoadFontEx`. Any new non-ASCII text needs its characters added in `assets.build_codepoints`, otherwise it renders as `?`.
 2. **Old font failure root cause**: `DroidSansJapanese.ttf` was a GitHub HTML page saved from a blob URL, not a font. Always download fonts from raw URLs and check them with `file`.
 3. **Thai shaping**: raylib does no text shaping, so Thai combining vowels/tone marks may be misplaced. Prefer standalone consonants on Thai cards.
-4. `odin.json` is not read by the Odin compiler (imports use relative paths); it is only informational.
+4. Tests share the memory game's global state, so they must run single-threaded (`just test` sets `ODIN_TEST_THREADS=1`).
+5. The game changes directory to the executable's folder at startup so `assets/` is found from anywhere.
 
 ## File Structure
 ```
 HanjaKanaMun/
 ├── AGENTS.md              # Project plan (this file)
 ├── README.md
-├── odin.json              # Informational only, not used by the compiler
+├── justfile               # build/run/check/test/package recipes
+├── ols.json               # ols language server settings (neovim)
+├── odinfmt.json           # odinfmt formatter settings (4 spaces, LF)
+├── .gitea/workflows/
+│   ├── gitea-build.yaml    # check + test + build on main/develop
+│   └── gitea-release.yaml  # package on version branches (*.*), upload to Gitea packages
 ├── main.odin              # Window/audio setup, screen state machine
 ├── src/
 │   ├── themes/themes.odin  # Theme struct, flag colors, Screen/Flag enums, layout constants
@@ -49,6 +55,7 @@ HanjaKanaMun/
 │   ├── card/card.odin      # Card struct, flag card-back art, face textures, flip animation
 │   ├── memory/memory.odin  # Memory game state, logic and drawing
 │   └── screens/screens.odin # Main menu and language menus
+├── tests/memory_test.odin  # Game logic and card animation tests
 └── assets/
     ├── MPLUSRounded1c-Medium.ttf
     ├── MPLUSRounded1c-ExtraBold.ttf
@@ -58,6 +65,6 @@ HanjaKanaMun/
 ## Notes
 - NO rm -rf or starting over
 - Make small, incremental changes
-- Test after each change (`odin check . -vet`, then run)
+- Test after each change (`just check`, `just test`, then `just run`)
 - Keep existing functionality working
 - Commit after each working step