init nix flake commit

flake.nix

@@ -0,0 +1,45 @@
+{
+  description = "ESP32-D0WD-V3 (esp32-hal) Rust dev flake";
+
+  inputs = { nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable"; };
+
+  outputs = { self, nixpkgs }: let
+    system = "x86_64-linux";
+    pkgs = import nixpkgs { inherit system; };
+  in {
+    devShells.${system}.default = pkgs.mkShell {
+      packages = with pkgs; [
+        llvm
+        cmake
+        ninja
+        python3
+        pkg-config
+        git
+        curl
+        wget
+        unzip
+        gcc
+        gnumake
+        rustup
+        cargo-espflash
+        espup
+      ];
+
+      shellHook = ''
+        echo ">>> ESP32 DevShell (esp-hal only)"
+
+        if [ ! -d "$HOME/.espup" ]; then
+          echo "Running espup install..."
+          espup install
+        fi
+
+        # Activate Xtensa Rust toolchain
+        export RUSTUP_TOOLCHAIN=esp
+        export PATH=$HOME/.rustup/toolchains/esp/bin:$PATH
+
+        echo "Xtensa Rust toolchain ready."
+        rustc --version
+      '';
+    };
+  };
+}