Update README.md

[noahho]

Issue

The Workflow decision tree has been missing some context.
TODO: Add KV caching

Public API Changes

• No Public API changes
• Yes, Public API changes (Details below)

[Copilot]

Pull Request Overview

This PR updates the README.md to improve the TabPFN workflow section by making the title more descriptive and adding clarifying content to guide users through the decision-making process.

• Enhanced the workflow section title to be more specific about its purpose
• Added descriptive text explaining how to use the decision tree for selecting appropriate TabPFN implementations
• Updated a flowchart node label to be more descriptive about handling large datasets

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[gemini-code-assist]

Code Review

This pull request updates the README.md file to improve the clarity of the TabPFN workflow section. The heading has been made more descriptive, a helpful explanatory paragraph has been added, and a node in the workflow diagram has been updated. These are good changes that enhance the documentation. I have one minor suggestion to improve the wording in the workflow diagram for better readability.