Add raw mode support to REPL for immediate key handling (Ctrl+L/Ctrl+C/Ctrl+D) and update README with usage notes

README.md

@@ -147,6 +147,10 @@ The interactive shell supports:
 
 See [examples/08_repl_guide.luash](examples/08_repl_guide.luash) for a comprehensive guide.
 
+Notes:
+- Raw terminal mode (immediate Ctrl+L/Ctrl+C/Ctrl+D) auto-enables when attached to a TTY.
+- Force enable/disable with `LUASH_RAW=1` or `LUASH_RAW=0`.
+
 ### Debug Mode
 ```bash
 LUASH_DEBUG=1 ./luash script.luash