Add Nix development environment and Claude guidance file

Change-Id: I4b3e2f0020409ee3f8b9e75633c901de94bd78d7
Signed-off-by: Thomas Kosiewski <tk@coder.com>

package.json

@@ -32,4 +32,4 @@
   "scripts": {
     "build": "bun build --target node --outfile dist/main.js ./src/main.ts --format cjs && sed -i '0,/^/s//#!\\/usr\\/bin\\/env node\\n/' ./dist/main.js"
   }
-}
+}