M0: flake + base NixOS config, rebuilt from repo on cc-ci

Pins nixpkgs to the rev cc-ci already ran (no-op-then-base); deploy via
switch --flake on-host. System healthy (gen 3) post-switch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flake.nix

@@ -0,0 +1,28 @@
+{
+  description = "cc-ci — Co-op Cloud recipe CI server (NixOS)";
+
+  inputs = {
+    # Pinned to the exact revision cc-ci already runs, so the first rebuild from
+    # this repo is a true no-op-then-base (M0). Bump deliberately, not drift.
+    nixpkgs.url = "github:NixOS/nixpkgs/50ab793786d9de88ee30ec4e4c24fb4236fc2674";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+    in
+    {
+      nixosConfigurations.cc-ci = nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = [ ./hosts/cc-ci/configuration.nix ];
+      };
+
+      # Devshell for working on the harness/bridge locally.
+      devShells.${system}.default = pkgs.mkShell {
+        packages = with pkgs; [ git jq curl nixpkgs-fmt ];
+      };
+
+      formatter.${system} = pkgs.nixpkgs-fmt;
+    };
+}