"Revolutionizing Event Processing: New Typeguards for Tier Purchases Unveiled!"

"Enhancements in type safety pave the way for seamless integration of on-chain events as development team rolls out critical updates."

Commit Details:

fix: add typeguards for TierPurchase onchain event (#2599) ## Why is this change needed? The typeguard for the new tier purchase event is required for processing these events cleanly out of the event stream. ## Merge Checklist _Choose all relevant options below by adding an `x` now or at any time before submitting for review_ - [x] PR title adheres to the [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) standard - [x] PR has a [changeset](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#35-adding-changesets) - [x] PR has been tagged with a change label(s) (i.e. documentation, feature, bugfix, or chore) - [x] PR includes [documentation](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#32-writing-docs) if necessary. <!-- start pr-codex --> --- ## PR-Codex overview This PR focuses on enhancing type safety by adding type guards for the `TierPurchaseOnChainEvent`, ensuring that the event structure is validated correctly. ### Detailed summary - Updated `TierPurchaseOnChainEvent` type in `packages/core/src/protobufs/types.ts` to include specific properties. - Introduced `isTierPurchaseOnChainEvent` type guard in `packages/core/src/protobufs/typeguards.ts` to validate `OnChainEvent` instances. > ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}` <!-- end pr-codex -->