[m-rosinsky]

Summary

• sync the public XChat Thrift schema with failure codes 10–18
• decode all known failure codes, including the previously unmapped code 9
• expose rate-limit tier metadata for RATE_LIMIT_UPSELL failures
• document the expanded Rust/JS event surface

Testing

• make ci

Notes

• committed Go static libraries were not regenerated; the prebuilt workflow should rebuild them from this core change.

[github-actions]

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I have read the CLA Document and I hereby sign the CLA

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1 out of 2 committers have signed the CLA.
✅ (santiagomed)[https://github.com/santiagomed]
❌ @m-rosinsky
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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ m-rosinsky
✅ santiagomed
❌ github-actions[bot]
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