feat(rag): install on m4 and amd, default endpoints to sgx

Add the rag CLI to the m4 and amd hosts and point its default API_BASE
and QDRANT_URL at sgx (where the gateway and Qdrant run) instead of
localhost. The services live on sgx, so a localhost default only worked
there; sgx resolves to itself on sgx, so this default is correct on every
host and leaves only RAG_API_KEY to set.

systems/aarch64-darwin/m4/default.nix

@@ -41,6 +41,7 @@ with lib.metacfg;
     claude-code
     opencode
     metacfg.pi
+    metacfg.rag
     defuddle-cli
     dnsmasq
     gh

systems/x86_64-linux/amd/default.nix

@@ -102,6 +102,7 @@ with lib.metacfg;
     azure-cli
     claude-code
     claude-desktop-with-fhs
+    metacfg.rag
     desktop-file-utils
     gnome-terminal
     gnome-remote-desktop