fix: add procps for Antigravity ps requirement

Author: duizendstra

src/antigravity-nix/install.sh

@@ -13,7 +13,8 @@ apt-get install -y --no-install-recommends \
     curl \
     ca-certificates \
     xz-utils \
-    gnupg
+    gnupg \
+    procps
 rm -rf /var/lib/apt/lists/*
 
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