[Advancement] Add branch protection documentation and contributor preflight script

[Nanle-code]

Objective

Document required branch protections and ship a preflight script that mirrors merge gates locally.

Target area

scripts/, CONTRIBUTING

Context

Contributors should know that PRs merge only with passing CI and no conflicts.

Requirements

• Document required status checks and conflict-free requirement
• Provide scripts/preflight-pr.sh running fmt/clippy/tests subset
• Link from CONTRIBUTING PR guidelines

Acceptance criteria

• Docs explicitly require all CI pass + no conflicts before merge
• Preflight script exists and is referenced
• Script exits non-zero on failures

Pull request merge requirements

Pull requests that resolve this issue must not be merged until all of the following are true:

1. All required CI checks are green on the latest commit of the PR (build, tests, lint/format, and any workflow jobs required by branch protection).
2. The branch has no merge conflicts with the target branch (master / default), and a clean merge or rebase is possible without unresolved conflicts.
3. Review feedback is addressed, and the change remains focused on this issue’s acceptance criteria.

Contributors should run the local CI-equivalent checks before opening or updating the PR (see CI_ENFORCEMENT.md and CONTRIBUTING.md).

[Godfrey-Delight]

@Godfrey-Delight has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer, I would love to work on this issue

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

[abbaskachia]

@abbaskachia has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi! I'd like to work on issue #807 if it's still available.

I’ll document the required branch protection and PR merge requirements, and add the contributor preflight script at scripts/preflight-pr.sh to run the relevant formatting, clippy, and test checks locally.

I’ll keep the changes focused on scripts/ and CONTRIBUTING, ensure the script exits non-zero when any check fails, and link the preflight process from the contributor PR guidelines.

Before submitting the PR, I’ll ensure the branch is up to date with the target branch, has no merge conflicts, and all required CI checks pass.

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

[drips-wave]

Congratulations, @Godfrey-Delight! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @Godfrey-Delight: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊

[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @Godfrey-Delight as part of the Stellar Wave Program's 8th Wave 🥳

Moderator's reason: [Auto-assessed] The pull request (#884) was successfully merged by the maintainers on 2026-08-30. It correctly implements the required branch protection documentation and provides the scripts/preflight-pr.sh preflight script as requested in issue #807.

😎 @Godfrey-Delight: You earned 100 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.

ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.