Add docs for event field types and Soroban encoding format

[Chucks1093]

Summary
Contract events carry fields encoded in Soroban XDR format, but the specific type mappings for each field are not documented. Indexers and consumers need to know whether a field is an Address, i128, Symbol, or other type to decode it correctly.

Scope

• document each field in every emitted event with its Soroban type and encoding format
• note any fields where the type differs from what the name implies
• place the docs alongside the event naming conventions reference

Acceptance Criteria

• every event field has a documented Soroban type
• any non-obvious type choices are explained
• no code changes are required; this is a docs-only issue

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[Chidubemkingsley]

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

would take this

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[Kingvic300]

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I would love to work on this

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[HassanKorey]

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

I would like to to work on the documentation of this issue

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[khanavi272-spec]

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I would like to work on this issue

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[Benedict315]

@Benedict315 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hello I would like to work on this issue

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Congratulations, @Benedict315! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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