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>

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "redactor"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+eframe = "0.31"
+