chore: add .gitignore for Zig artifacts, generate-clades script

- Add zig-out/, zig-cache/, .zig-cache/ to .gitignore
- Move generate-clades heredoc to scripts/generate-clades.sh (justfile compat fix)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.gitignore

@@ -18,6 +18,11 @@ Thumbs.db
 /dist/
 /out/
 
+# Zig
+zig-out/
+zig-cache/
+.zig-cache/
+
 # Dependencies
 /node_modules/
 /vendor/