fix(rsc): fix transformWrapExport with filter and rejectNonAsyncFunction

[james-elicx]

Updated description by @hi-ogawa

transformWrapExport currently validates filter-ed exports and includes them in exportNames even though their values are not wrapped. It also makes metadata exports fail async validation and reports references that were never registered.

This behavior wasn't a problem for rsc plugin's internal use for rsc css transform https://github.com/vitejs/vite-plugin-react/blob/main/packages/plugin-rsc/README.md#css-support, but is a problem for more general usages such as the integration indicated in #1246.

This PR fixes transformWrapExport so that filter and rejectNonAsyncFunction options and exportNames return value behaves naturally and consistently. It also refines ExportMeta.isFunction: boolean | undefined detection so filter can make use of it more flexibly. The new test is added to cover hopefully all possible patterns of ExportMeta.

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Original description

Extracted from #1246.

transformWrapExport currently validates filtered exports and includes them in exportNames even though their values are not wrapped. This makes metadata exports fail async validation and reports references that were never registered.

This applies filtering before validation/reporting and keeps unresolved identifier exports eligible for wrapping. Tests cover named exports, default exports, and unknown identifier metadata.

[hi-ogawa]

Hey, thanks for the fix! This looks like a nicely scoped change, so I've adjusted a bit and will be merging. Will try to capture larger picture as I go through other PRs.