Closes #14472

Introduces `workspace::ZoomIn` and `workspace::ZoomOut` actions that
complement the existing `workspace::ToggleZoom` action. ZoomIn only
zooms if not already zoomed, and ZoomOut only zooms out if currently
zoomed. This enables composing zoom actions with
`workspace::SendKeystrokes` for workflows like "focus terminal then zoom
in".


<details><summary>Example usage</summary>
<p>

Example keybindings:

```json
[
  {
    "bindings": {
      "ctrl-cmd-,": "terminal_panel::ToggleFocus",
      "ctrl-cmd-.": "workspace::ZoomIn",
    }
  },
  {
    "context": "Terminal",
    "bindings": {
      "cmd-.": "terminal_panel::ToggleFocus"
    }
  },
  {
    "context": "!Terminal",
    "bindings": {
      "cmd-.": ["workspace::SendKeystrokes", "ctrl-cmd-, ctrl-cmd-."]
    }
  },
]
```

Demo:


https://github.com/user-attachments/assets/1b1deda9-7775-4d78-a281-dc9622032ead

</p>
</details> 



Release Notes: 

- Added the actions: `workspace::ZoomIn` and `workspace::ZoomOut` that
complement the existing `workspace::ToggleZoom` action