Fix test runner: switch from tsx --test to vitest

[isaacsight]

The test script in packages/kbot/package.json uses tsx --test but 26/27 test files import from vitest. 12 of 24 test files fail. Change the test script to vitest run and ensure vitest is a devDependency.

[isaacsight]

Fixed in d904641 — test script changed to vitest run, 698 tests passing.