Write `tests/e2e/README.md` covering E2E setup and test authoring guide

[Nursca]

Description
New contributors who want to add E2E tests have no guide. Without documentation, they are likely to break the test setup or duplicate existing helper utilities.

Requirements and context

• Cover: prerequisites, how to run E2E tests locally, how the Docker node setup works, how to write a new test (with annotated example), available test helpers (funding accounts, ledger advance, indexer polling), how to debug a failing test
• Document the global setup sequence and teardown

Suggested execution

git checkout -b docs/e2e-readme

• Create tests/e2e/README.md
• Link from org root README.md

Example commit message
docs(e2e): write E2E setup guide and test authoring documentation

[midenotch]

@midenotch has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I've reviewed the issue and understand the requirements. I'd love to work on this and submit a clean PR that meets the acceptance criteria.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @midenotch to this issue.

[distributed-nerd]

@distributed-nerd has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i work on this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @distributed-nerd to this issue.

[grantfox-oss]

🦊 GrantFox — @distributed-nerd has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #287)
2. Your PR will be reviewed by the Invoice-Liquidity-Network maintainers

Good luck! Track your progress on GrantFox.

[drips-wave]

Congratulations, @distributed-nerd! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @distributed-nerd: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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