Chain shide commands

There could be some middleware-like system where you can have a global and local shide command with the same name, and one yields to the other if it can't handle the command. Likely `shide.next()`.

Alternative:

```js
shide.call('some-command', {})
shide.call('some-command', {
local: true,
args: { foo: 'bar' },
});
```

This seems cleaner.

Start by locating the existing command-dispatch entry point and reviewing how global and local commands are currently resolved. Compare the proposed shide.next() and shide.call() approaches, then define the expected fallback behavior, command scope, and arguments before implementation. Done means the chosen API and delegation rules are agreed and covered by appropriate tests.

Written by the indexing model from the issue text.