feat(app2,ts-sdk): add reactive Effect utilities for Svelte 5 (#4444)

**New Features:**
- `runFork` & `runForkWithRuntime` provide a `Fiber` reference and
interrupt function.
- `runPromiseExit` & `runPromiseExitWithRuntime` provide a reactive
`Exit` value, an interrupt function, and a reactive `Either` marshaller.
- All utilities perform automatic `Fiber` interruption as part of
`$effect` cleanup.

**Additional Changes:**
- `effect` dependencies updated to latest; checked to ensure no runtime
version mismatch.
- `vite`/`vitest` hoisted into workspace for consistency (and to resolve
issue preventing `vite.config.ts` to declare `test` configuration in
`UserConfigExport` declaration).
- [`happy-dom`](https://github.com/capricorn86/happy-dom) preferred over
`jsdom` because performance (note we do not yet make use of DOM-reliant
testing).