Add metacircular control programs to rift, orion, and vade

Install mciasctl, mciasgrpcctl, mcrctl, and mcproxyctl via new
configs/mcpkg.nix module. Adds flake inputs for mcias, mcr, and
mc-proxy from git.wntrmute.dev.

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

configs/mcpkg.nix

@@ -0,0 +1,9 @@
+{ inputs, ... }:
+
+{
+  environment.systemPackages = [
+    inputs.mcias.packages.x86_64-linux.default
+    inputs.mcr.packages.x86_64-linux.default
+    inputs.mc-proxy.packages.x86_64-linux.default
+  ];
+}