docs: add memory guide quick try

[RerankerGuo]

Fixes #2081.

Summary

• Add a small optional quick-try note before the local plugin install steps.
• Keep the local-first setup path as the primary flow.

Validation

• Confirmed the quick-try URL returns HTTP 200.
• Confirmed the README still keeps Quick Start followed by 1. Install as the main setup flow.
• make format could not run locally because poetry is not installed: make: poetry: Command not found.