Adds the missing `morph <target> to <html>` command. Runtime includes a small
HTML fragment parser that applies the outer element's attributes to the target,
rebuilds children, and re-activates hyperscript on the new subtree. Other
hyperscript fixes (^ attr ref, dom-ref keyword, pick keyword, between in am/is,
prop-is removal) from parallel work are bundled along.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>