Initial push

.envrc

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+use flake

flake.nix

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+{
+  description = "chess_interface Development Environment";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+    zig-overlay.url = "github:mitchellh/zig-overlay";
+    zig-overlay.inputs.nixpkgs.follows = "nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, zig-overlay, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            zig-overlay.overlays.default   # <-- use the flake overlay, NOT (import zig-overlay)
+          ];
+        };
+      in {
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            zigpkgs.master   # Zig nightly (“master”)
+            zls              # Zig LSP (optional)
+          ];
+
+          ZIG_GLOBAL_CACHE_DIR = ".zig-cache-global";
+
+          shellHook = ''
+            echo "Welcome to the chess_interface dev env (${system})"
+            echo "Zig: $(zig version)"
+          '';
+        };
+      });
+}