chore: add linguist overrides to prevent Makefile language detection

Replace Makefile entry with Justfile/justfile/Mustfile linguist-language
overrides in .gitattributes so GitHub correctly identifies the build
system language instead of showing "Makefile".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Jonathan D.A. Jewell

.gitattributes

@@ -33,8 +33,9 @@
 # Config
 .gitignore     text eol=lf
 .gitattributes text eol=lf
-justfile       text eol=lf
-Makefile       text eol=lf
+Justfile       text eol=lf linguist-language=Just
+justfile       text eol=lf linguist-language=Just
+Mustfile       text eol=lf linguist-language=YAML
 Containerfile  text eol=lf
 
 # Scripts