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fix(web): spread applies attributes before children, matching ssrElement (#3741) (#3757)

A dynamic() / <Dynamic> element whose prop getter mints a hydration id (a
ternary over a signal compiles to a condition memo inside the getter) and
whose children include an element hydrated with a key miss: the client's
runtime spread() inserted `children` before its attribute effect read the
getters, while the server's ssrElement read attributes first. Both draw on
the enclosing component's id counter, so the memo and the child element
swapped ids and the server's child was never claimed.

spread() now creates its attribute effect before the children insert -- the
order a compiled element already uses (its spread/attribute effects precede
its children inserts). ssrElement defers reading a `children` prop until
after every attribute (and the trailing compiled attribute thunk), so a
`children` key listed before an id-minting attribute agrees too.

Side effect on the client: a ref on a dynamic() element now runs before its
children are inserted, as on a compiled element.

Size: page: base +59 B brotli (+1 B minified), layout only; frozen cap
raised 46.20 -> 46.24 KB with a Size-Exception note.

Fixes #3741

Co-authored-by: Claude via Cursor <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

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