docs(examples): add financial-research scaffold README

[kaiicheng]

Summary

Add an initial scaffold README for a future financial-research example under examples/.
The goal is to establish a starting point for a finance-oriented ArkSim example focused on research and analysis workflows.

Changes

• added examples/financial-research/README.md
• described the intended use cases for the example
• documented the current scope and possible future additions

Documentation

• No additional docs needed (this PR only adds an example scaffold README)

How to Test

• Manual verification: verified that examples/financial-research/README.md is included in the PR diff

Notes

This PR is intentionally minimal and only introduces the initial scaffold.
Future follow-ups may add configs, scenarios, metrics, and runnable example assets.

[itsarbit]

Hey Kai, thanks for putting this together. I think the financial research use case is interesting, but this PR is more of a design proposal than a working example.

Our pattern for examples in this repo is: working code (config.yaml, custom_agent.py, scenarios.json) shipped together with a README that shows how to run it. This README has the setup section commented out and no actual code to go with it.

Would you be open to converting this to a GitHub Discussion instead? That way we can iterate on the design together, and once the implementation is ready, open a proper PR with code + docs together. Happy to help spec it out in the discussion.