fix: Add missing run.sh script for x402 sample

[Ayush10]

Summary

• Adds a dedicated run.sh script to samples/python/scenarios/a2a/human-present/x402/ with PAYMENT_METHOD="X402" as the default, matching the pattern of the existing cards/run.sh.
• Updates the x402 README.md execution instructions to reference the new local script instead of cards/run.sh --payment-method x402.

Closes #107

Test plan

• Run samples/python/scenarios/a2a/human-present/x402/run.sh and verify all agents start with PAYMENT_METHOD=X402
• Confirm the script behavior matches cards/run.sh --payment-method x402

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[gemini-code-assist]

Summary of Changes

Hello @Ayush10, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the developer experience for the x402 payment sample by introducing a dedicated shell script for its execution. This change streamlines the setup and running process, making the sample more consistent with other examples and reducing manual configuration steps for users.

Highlights

• New dedicated run script: A new run.sh script has been added to samples/python/scenarios/a2a/human-present/x402/ to automate the execution of the x402 payment example, mirroring the structure of other sample scripts.
• Default payment method: The newly added run.sh script for x402 sets PAYMENT_METHOD="X402" as its default, ensuring correct configuration for the sample.
• README update: The README.md for the x402 sample has been updated to reflect the new run.sh script, simplifying execution instructions for users.

🧠 New Feature in Public Preview: You can now enable Memory to help Gemini Code Assist learn from your team's feedback. This makes future code reviews more consistent and personalized to your project's style. Click here to enable Memory in your admin console.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces a dedicated run.sh script for the x402 sample, aligning it with the structure of other samples and simplifying the execution process. The changes also include updating the README.md to reflect this new script. The implementation is solid, but I have a couple of minor suggestions for the new shell script to enhance its robustness by following shell scripting best practices.

[Ayush10]

Thanks for the review! The first suggestion (quoting $1) is already applied in this PR. The second suggestion about quoting $AGENTS_DIR — it's already quoted on line 137. No additional changes needed here.