[Feature]: Allow `openshell sandbox connect` to accept command arguments

[nv-ddave]

Description

openshell sandbox connect only opens an interactive shell. It does not accept command arguments for non-interactive execution.

Proposal

# Current (interactive only)
openshell sandbox connect my-assistant

# Proposed (also support non-interactive)
openshell sandbox connect my-assistant -- echo hello
openshell sandbox connect my-assistant -- python3 /sandbox/script.py

Context

This is related to the openshell sandbox exec proposal. Both solve the same problem — running commands without an interactive shell. The connect -- <command> pattern follows SSH conventions (ssh host -- command).