Docs: reconcile architecture docs with actual repo layout

[Otaiki1]

Build location

Work primarily in docs/ARCHITECTURE.md. Keep related tests/docs beside that package unless this issue explicitly calls for a cross-package update.

Why this matters

Architecture docs still describe contracts as a separate repo and include idealized structures that may drift from current packages.

What to build

• Audit docs/ARCHITECTURE.md against client, sdk, backend, indexer, oracle, and docs directories.
• Mark external contract assumptions clearly.
• Add an updated package responsibility map.

Acceptance criteria

• Docs identify actual build locations for major features.
• Outdated paths are removed or clearly labeled as planned.

Suggested verification

Run the affected package checks listed in this issue, plus the root build when the change crosses package boundaries.

[ShantelPeters]

@ShantelPeters has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

i would like to work on this issue , kindly assign please

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

[drips-wave]

Congratulations, @ShantelPeters! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @ShantelPeters: 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 🌊