- Simple `bun test` should also work now
- Added tests for Dynamic and Portal
- Brought in universal renderer for custom addAnchorNode logic
- Fixes a bunch of bugs around Show and For 
- We throw on not adding unwrapped text/span.

…eplacement

The forked universal renderer diverged from solid-js's upstream behavior
in cleanChildren(). When called without a marker or replacement (e.g.
when Show/Switch hides content), it returned `replacement` which is
`undefined`, instead of returning "" like solid-js does.

This caused undefined to propagate through the reactive graph as the
`current` value in insertExpression, eventually corrupting downstream
memo reads.

Introduced in #169 when the universal renderer was forked.

…eplacement (#670)

## Summary

- Fix `cleanChildren` in the forked universal renderer to return `""`
instead of `undefined` when called without a replacement, matching
solid-js's upstream behavior

## Problem

When `cleanChildren` is called without a `marker` or `replacement` (e.g.
when `Show`/`Switch` hides content), the no-marker early-return path
returns `replacement` — which is `undefined`. The solid-js upstream
returns `""`.

This `undefined` propagates as the `current` value through
`insertExpression`'s reactive chain, eventually corrupting downstream
memo reads and causing crashes like:

```
TypeError: undefined is not an object (evaluating 'grouped().length')
```

Introduced in #169 when the universal renderer was forked from solid-js.

## Fix

```diff
- return replacement
+ return replacement ?? ""
```