chore: upgrade Vitest from 3.x to 4.x to fix flaky CI onTaskUpdate timeout

[solidsnakedev]

CI intermittently fails with:

Error: [vitest-worker]: Timeout calling "onTaskUpdate"

All tests pass but the unhandled error makes the run exit with code 1. This is a known Vitest 3.x bug where the birpc RPC channel between the main process and test worker has a hardcoded 60s timeout that fires independently of testTimeout. Under CI resource pressure, the worker blocks long enough to trigger it.

Fixed upstream in vitest-dev/vitest#8297 (merged Jul 2025), first available in v4.0.0-beta.4. Latest stable is v4.0.18.

Upgrade scope:

• vitest: ^3.2.4 → ^4.0.18
• @vitest/coverage-v8: ^3.2.4 → ^4.0.18
• @effect/vitest: ^0.25.1 → compatible version for vitest 4.x
• Verify all 971 unit tests pass
• Verify devnet tests pass
• Check for any breaking API changes in vitest 4.x

[danbaruka]

Hi @solidsnakedev,
I’d be happy to take this issue and start working on it. Please let me know if it’s available to assign.

Thanks!