Initial commit: two-pane text redaction GUI

Rust/egui app with Nord theme and embedded Brass Mono font.
Left pane for editable source text, right pane shows redacted preview.
Select text and Ctrl+R to toggle redaction (whitespace preserved).
Ctrl+Q to quit, copy-redacted button for clipboard export.
Includes Nix flake devshell and direnv integration.

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

flake.nix

@@ -0,0 +1,57 @@
+{
+  description = "A simple text redaction GUI tool";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs { inherit system overlays; };
+        rust = pkgs.rust-bin.stable.latest.default;
+
+        nativeBuildInputs = with pkgs; [
+          rust
+          pkg-config
+        ];
+
+        buildInputs = with pkgs; [
+          # egui/eframe dependencies
+          libxkbcommon
+          libGL
+          wayland
+          libx11
+          libxcursor
+          libxrandr
+          libxi
+          vulkan-loader
+        ];
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          inherit nativeBuildInputs buildInputs;
+
+          LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath buildInputs;
+        };
+
+        packages.default = pkgs.rustPlatform.buildRustPackage {
+          pname = "redactor";
+          version = "0.1.0";
+          src = ./.;
+          cargoLock.lockFile = ./Cargo.lock;
+          inherit nativeBuildInputs buildInputs;
+
+          postFixup = ''
+            patchelf --set-rpath "${pkgs.lib.makeLibraryPath buildInputs}" $out/bin/redactor
+          '';
+        };
+      }
+    );
+}