test(rsc): add persistent use cache example

[hi-ogawa]

• closes Add use cache example with external persistence beyond in-memory store #1409
• closes Research "use cache" cache invalidation strategy during dev #1395

TODO

The existing use cache examples keep entries in function-keyed memory, which naturally loses them when a transformed module is reevaluated and does not expose persistent-cache invalidation requirements.

This PR adds a standalone file-level use cache example with a filesystem-backed handler and self-contained Flight values. A development module generation and reverse-importer hotUpdate traversal invalidate entries after cached function, direct dependency, and transitive dependency edits.