Fallback for serial USB drive helpers

[makermelissa-ai-assistant]

Summary

• fall back to inline CircuitPython snippets when circuitpython-repl-js does not expose tryDisableUsbDrive() / enableUsbDrive()
• preserves serial file transfer for supported beta firmware such as 10.3.0-alpha builds even when the bundled REPL helper API is unavailable

Testing

• npm run build
• git diff --check

Notes

Console error observed before this fix:

Unable to disable the CIRCUITPY USB drive: TypeError: this.repl.tryDisableUsbDrive is not a function

[makermelissa]

We're not going this route because it circumvents the advantage of putting the code in circuitpython-repl-js. It would require any code changes in 2 places.