Documented layout values now actually apply

The layout documentation has always shown stack gaps as CSS lengths ("8px", "1rem") and alignments as lowercase words ("start", "center", "end"). Following it did not work: the client-side conversion parsed a gap as a plain integer and an alignment with an exact-case match, so both of those documented values failed to convert, were replaced by the default, and left an error line in the log on every render.

Sizes now accept a CSS unit — px, %, rem, em and the rest of the CSS set — and alignment and orientation words are matched without regard to case. Numbers are read the same way everywhere in the world: "1.5" is one-and-a-half whether or not the server happens to sit in a comma-decimal locale.

A value that genuinely cannot be read no longer throws mid-render. It falls back to the property's default, which is what a viewer already saw, without tearing down the live binding for the rest of the page.