Add CI step that asserts `EVENT_SCHEMA.md` includes one row per `env.events().publish` site (grep gate)

[greatest0fallt1me]

Description

We want a mechanical gate: count env.events().publish( sites across the three crates and require EVENT_SCHEMA.md to mention each topic. Fails the CI build if a new emit is added without a doc entry.

Requirements and Context

• New scripts/check_event_schema_coverage.sh
• Wire into .github/workflows/*.yml
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b ci/event-schema-coverage-gate

2. Implement changes
   • scripts/check_event_schema_coverage.sh
   • Workflow update
3. Test and commit
   • Run script locally and confirm pass; intentionally add a fake publish to confirm fail
   • Include test output and notes in the PR

Example commit message

ci: gate event schema coverage against publish-site count

Acceptance Criteria

• Script reports clear diff when topics missing from EVENT_SCHEMA.md
• CI fails on missing entries
• Handles #[cfg(test)] blocks correctly (excluded)

Guidelines

• .rs only under contracts/.../src/ if any; NatSpec-style /// doc comments
• Use real Soroban SDK idioms
• Clear documentation and inline comments
• Timeframe: 96 hours

[temisan0x]

@temisan0x has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Please can I work on this?

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@temisan0x's PR #466 was approved and merged by @greatest0fallt1me.

🏆 @temisan0x: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (891 total points). Track your full progress on GrantFox.

👏 Great work, @temisan0x! Keep contributing to CalloraOrg.

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This issue has been completed by @temisan0x as part of the Stellar Wave Program's 6th Wave 🥳

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