Provided we decide to keep the global activity action in the bottom of the activity bar, I suggest to tackle some debt associated with it:

• we introduce a new registry for global activity which seems odd, instead I suggest to use the already existing GLOBAL scope within IActionBarRegistry that can be used to register an action bar contributor for this scope. the activity bar part can then easily read out those actions from the global scope and use them
• instead of introducing a new type IGlobalActivity that has to return actions that will show on click in the context menu we should just register an instance of IAction that inside its run method shows actions using the context menu service

Given these changes, I think we no longer need activity.ts and we basically have the old concept we used to have which is to register a global action that just implements everything through the run method.

/cc @joaomoreno