feat(typescript): add useRow hook for Vue and React to fix issue #5060

[rohanranjan0902]

Description of Changes

Added a new useRow hook for the React and Vue bindings to provide a cleaner developer experience when querying single rows or views that return t.option().

Previously, because the SpacetimeDB host runtime represents all views as tables, the client-generated SDK would type t.option() views as returning an array. This forced developers to manually unwrap the array (e.g. userData?.value[0] ?? undefined). The new useRow hook wraps useTable and automatically returns the first element or undefined.

Fixes #5060

API and ABI breaking changes

None. This is purely an additive feature for the client SDKs.

Expected complexity level and risk

1

This is a trivial, additive change. It simply introduces a thin wrapper around the existing useTable hook to extract the first element.

Testing

• Verified the TypeScript bindings compile without errors via pnpm run build locally.
• Reviewers can check that useRow functions as intended in an actual React or Vue app when subscribing to a table or view.

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