FF Expert: Natural language acknowledgement of already-installed packages

## Problem

While FF Expert now shows a "manage" button for packages that are already installed (implemented in #6536), it doesn't explicitly acknowledge in its natural language responses that it knows a recommended package is already installed.

When a user asks "How do I work with Modbus data?" and `node-red-contrib-modbus` is already installed, the expert could enhance the UX by saying something like "I can see you already have node-red-contrib-modbus installed..." rather than treating it the same as packages that need installation.

## Discussion Points

From #6536, @Steve-Mcl raised valid concerns about implementation cost:
- Would require additional system prompts
- Need to either:
1. Always pass packages in every chat request, or
2. Have intent analysis, or
3. A conditional tool entry in the graph that detects "modules were returned" to request modules and compare

**Decision:** Let's first feel the UX of the current iteration (manage button) before committing to this enhancement.

## Potential Solution (if pursued)

If user feedback indicates this would significantly improve the experience:
- Update FF Expert system prompts to acknowledge installed packages
- Implement one of the three approaches above to make package context available
- Ensure responses naturally reference "the \[package] you already have installed" when appropriate

## Acceptance Criteria

- [ ] FF Expert responses explicitly mention when recommended packages are already installed
- [ ] Natural language feels conversational (e.g., "I can see you have X installed...")
- [ ] Implementation cost is justified by UX improvement

## Related Issues

- Blocked by: #6536 (FF Expert: Consume and utilize package information)
- Parent: #6502 (FF Expert context awareness)
- Roadmap: https://github.com/FlowFuse/product/issues/2