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>

.claude/settings.local.json

@@ -0,0 +1,7 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(cargo init:*)"
+    ]
+  }
+}