Command palette (cmd-k) doesn't really work with commands

Previously: #138

AFAIK, the command palette (cmd-k) technically does offer some very basic commands, e.g. "Go to Home". That said, it mostly centres around documents. Indeed, as soon as I type something in it, the results only cover documents and not actions.

I suggest that we reach one of the following states:

1. Make it a "search palette" only
- Rename it, avoiding the term "command" everywhere
- Remove any actions
2. Make it a proper "command" palette
- Expand the range of available actions
- Include contextual ones, e.g. "Delete" and "Rename" should be available when the current view is a document
- Fix searching

No files, tests, or entry points are named. Start by locating the cmd-k command palette implementation and checking how it currently searches documents and exposes actions. Done requires an agreed direction—search-only or a fuller command palette—along with defined actions and working search behavior.

Written by the indexing model from the issue text.