docs: Clarify financial tool description in README

[weklund]

Reworded a sentence for clarity and conciseness.

Summary

Changes

Testing

• Tested with real transaction data (or describe sample data used)
• Skills activate correctly when invoked
• No hardcoded user-specific values

Data Safety Checklist

• I have NOT included any personal financial data in this PR
• I have NOT modified CLAUDE.md with personal information (income, debts, balances, goals)
• No files from data/ or reports/ are included in the diff
• No .db or .sqlite files are included in the diff
• I have checked git diff for account numbers (***NNNN), dollar amounts in context sections, or other PII
• If I forked this repo and used it with my own data, I have verified none of that data leaked into this PR

Type

• New skill
• Bug fix
• Bank parser
• Framework/documentation
• Other