Additional helpers preparing Virtual Raindex for usage in RaindexClient

[hardyjosh]

Caution

This PR is chained to #2175

Motivation

• Virtual snapshots were export-only; the client needs import/replay support.
• We also need first-class cache ingestion APIs and wasm-friendly serialization.

Solution

• Add serde-friendly snapshot bundle types + VirtualRaindex::from_snapshot[_bundle].
• Extend StaticCodeCache with validated upserts, bulk loaders, and new error variants.
• Cover snapshot/cache round trips in tests (with wasm smoke guard)

Checks

By submitting this for review, I'm confirming I've done the following:

• made this PR as small as possible
• unit-tested any new functionality
• linked any relevant issues or PRs
• included screenshots (if this involves a front-end change)

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch 2025-10-03-vr-live-quote

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[rouzwelt]

I noticed the [allow(unexpected_cfgs)] at top of the file, but don't think #[cfg(wasm_test)] works here?
as I don't see any changes to the flake command nor the ci steps commands, and didn't find anything about this cfg in the wasm-bindgen docs either, so I don't think this test is running at all by the wasm test flake command and actually I think it doesn't even compile. as I checked the workflow runs and didn't find this test running at all in the logs either.

for that to run this test, we need to include this crate in the command and set this cfg to normal test and if its only suppose to run in wasm env, it should be configured through target_family = wasm as far as I know