FF Expert to command direct installation of offered package

**Parent Deliverable:** FlowFuse/product#47 — Expert as Agentic Co-pilot

### Description

FF Expert offers node packages for installation. Currently it opens the manage palette. The task here is to directly install. This will depend on sister issue in nr-assistant.

- the "Install" button on ff-expert should have a spinner that indicates installation is occurring
- requires promise based comms from ff-expert to nr-assistant (succeed or fail)
- the "Install" button should reactively update to "Manage" (due to vuex palette state)

Refer to parent issue for more detail

### Epic/Story

_No response_

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate