Add 'tool_names' field to SimilarityAnalysisRequest

[aponcedeleonch]

Add tool_names: list[str] to SimilarityAnalysisRequest in src/mcp_malt/models/schemas.py such that clients can scope down the analysis to specific tools exposed by the MCP servers.

Aside from a general usability improvement, this will remedy the difficult to work around failure in get_recommendations in src/mcp_malt/api/similarity.py (fails if the MCP servers don't have exactly two tools)

Also update corresponding cli code.