Embed fonts into the executable, ship release artifacts as bare binaries

Fonts are now baked in with #load and loaded via LoadFontFromMemory
instead of LoadFontEx reading assets/*.ttf from disk, so a build no
longer needs an assets/ folder next to it at runtime - the chdir to
the executable's own directory in main.odin is dead code, removed.

just package / just package-windows now produce a single executable
(build/<name>_<version>_<os>_<arch>[.exe]) instead of a tar.gz/zip,
and the release workflow's upload/release-asset globs and the lld/zip
toolchain package list are updated to match.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -28,9 +28,9 @@ Requires [Odin](https://odin-lang.org) (dev-2026-09) and [just](https://just.sys
 just run              # build and play (debug)
 just check            # type-check with -vet
 just test             # run tests
-just package 1.0      # native release build -> build/HanjaKanaMun_1.0_<os>_<arch>.tar.gz
+just package 1.0      # native release build -> build/HanjaKanaMun_1.0_<os>_<arch> (self-contained executable)
 just windows-deps     # Linux only: fetch Windows SDK/CRT (xwin) and raylib.lib
-just package-windows 1.0  # cross-compiled Windows build -> build/HanjaKanaMun_1.0_windows_x86_64.zip
+just package-windows 1.0  # cross-compiled Windows build -> build/HanjaKanaMun_1.0_windows_x86_64.exe
 ```
 
 The Windows build needs `lld-link`. On macOS, `brew install lld` and set `LLD_LINK`, and point `XWIN_SDK` and