Monitor command passthrough

## Description

VICE's text monitor supports many commands beyond what the BMP protocol exposes directly (e.g., `d` for disassembly, `m` for memory dump, `io` for I/O register display, `load`/`save` for files). Exposing a command passthrough would let advanced users run arbitrary monitor commands from Ghidra.

## Proposed implementation

- Add a remote method `monitor_command(process: C64, command: str)` that sends a text command to VICE
- Display the text response in Ghidra's console or as a popup
- Note: the BMP protocol's support for text commands is not fully documented; may need to use the text monitor socket instead of BMP

## Why this matters

Power users familiar with VICE's monitor could use Ghidra as a frontend without losing access to advanced monitor features.