Update flake.nix to use latest Rust toolchain

README.md

@@ -104,10 +104,23 @@ flatpak run org.example.rustdevshell
 
 This project is configured for seamless flashing from the IDE or terminal.
 
+### Troubleshooting: No Connected Probes
+
+If you encounter the error `Error: No connected probes were found` or udev rule warnings, check the following:
+
+1.  **Hardware Connection**: Ensure your Raspberry Pi Pico W is connected via a compatible debugger (e.g., another Pico running `picoprobe`, a CMSIS-DAP debugger, or an ESP-Prog).
+2.  **Udev Rules (Linux)**: `probe-rs` needs permission to access the USB device.
+    -   Create a file named `/etc/udev/rules.d/69-probe-rs.rules`.
+    -   Add the rules provided by the [probe-rs documentation](https://probe.rs/docs/getting-started/probe-setup/).
+    -   Reload rules: `sudo udevadm control --reload` and `sudo udevadm trigger`.
+3.  **Group Membership**: Ensure your user is in the `plugdev` or `dialout` group (depending on your distro's udev rules).
+
 ### Flashing from IDE
 
 If you are using **RustRover** or **IntelliJ Rust**, you can use the "Flash Pico W" run configuration provided in the `.run` folder. Just select it from the run menu and click "Run".
 
+**Note:** The project is configured to use `direnv exec .` in `.cargo/config.toml` to ensure `probe-rs` is available. Ensure `direnv` is installed and allowed (`direnv allow`) on your system. For the best experience, we recommend installing the **direnv** plugin for your IDE.
+
 ### Flashing from Terminal
 
 You can flash the Pico W by running: