[Tests] Add unit tests for XAISpeechToTextDriver

[Salazareo]

XAISpeechToTextDriver.ts has no tests. Add an offline XAISpeechToTextDriver.test.ts (separate from any future integration test) covering audio input handling, model selection, response shape, error paths, and cost reporting via costs.ts.

[kryputh]

Hey @Salazareo I came across this and I think I am capable of handling and implementing the issue can you assign the issue to me...

I want to contribute

[Salazareo]

hi @kryputh thanks for helping out! I've assigned this to you.

Just for some advice on this, you can take a look at some of the other tests we've started adding like https://github.com/HeyPuter/puter/blob/main/src/backend/drivers/kv/KVStoreDriver.test.ts

Generally we just try to mock data over the methods where possible, but with ai services you'll likely need to mock the ai service call itself.

I've found agents like claude or codex are pretty good at bootstrapping these tests, if you've got access to them