Soroban event topic indexing strategy review (post-v2 audit)

[truthixify]

Tier: M (2-4 days) Type: audit

Context

Now that v2 announcer is live, we should audit whether the chosen topic layout was optimal and whether any of the other 5 contracts could benefit from similar indexing.

Scope

• Review event topics emitted by each Stellar contract
• For each event with high read volume: assess whether better topic indexing would help indexers
• Produce stellar/EVENT_INDEXING_AUDIT.md with findings
• For any recommended change, file a follow-up issue

Acceptance criteria

• Audit document committed
• Per-contract findings
• Concrete follow-up issues for any recommended changes
• Sign-off that v2 announcer schema is final

Files to start with

• stellar/EVENT_TOPIC_DESIGN.md
• All stellar/*/src/lib.rs