Feature: All cmds should be under a single Opencode cmd

[cameronr]

As discussed in #43, all : cmds should be under a single Opencode cmd to keep the cmd namespace clean.

Here's my proposal for the commands:

Structure:

:Opencode [subcommand] [args]

Proposed Subcommands:

:Opencode " Toggle (default action)
:Opencode open [input|output]
:Opencode close
:Opencode cancel             " Renamed from stop, cancels current request, if there is one
:Opencode toggle             " Toggle open/close
:Opencode toggle_focus        " Toggle focus between opencode and code window
:Opencode toggle_pane         " Toggle between input/output panes
:Opencode swap

" Session Management
:Opencode session new [title]
:Opencode session select
:Opencode session child
:Opencode session compact
:Opencode session share
:Opencode session unshare
:Opencode session agents_init " Renamed from init, analyze app and create AGENTS.md

" History
:Opencode undo
:Opencode redo

" Diff/Review
:Opencode diff [open|next|prev|close]
:Opencode revert all [prompt|session|snapshot]
:Opencode revert this [prompt|session|snapshot]
:Opencode restore file <snapshot>
:Opencode restore all <snapshot>

" Agent/Mode
:Opencode agent [plan|build|select]
:Opencode models

" Utilities
:Opencode run <prompt>
:Opencode run_new <prompt>
:Opencode help
:Opencode mcp

" Permissions
:Opencode permission [accept|accept_all|deny]

Notes: use snake_case for multi-word sub-cmds and arguments.

Open questions

• Is backwards compatibility important? Yes, with a warning
• Are there any commands missing or any that we can remove?

[sudo-tee]

For backward compatibility we probably should emit a warning and remove the code later ?

This is why I think we should start thinking about versioning the plugin. It would make this easier.