chore: gitignore zig-out and .so, untrack libgateway.so

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

Author: hyperpolymath

.gitignore

@@ -73,6 +73,14 @@ htmlcov/
 *.log
 /logs/
 
+# Zig
+ffi/zig/zig-out/
+**/.zig-cache/
+
+# Shared libraries
+*.so
+*.dylib
+
 # Temp
 /tmp/
 *.tmp