fix(compiler): scope-wrap dynamic children holes in the ssr spread path - #540

The hole-owner-id-scopes change added the ssr generate's scope() wrap in
transformChildren (the template path) but never in createElement, the
spread-element path that renders through ssrElement. The dom generate
scope-wraps the matching insert accessor regardless of spread, so a shape
like <a {...props}>{children()}</a> reserved a hydration id slot on the
client but not on the server — every hydration key allocated after the
hole drifted and following siblings went unclaimed (duplicated DOM,
'unclaimed server-rendered node' warnings). Hit in practice upgrading
TanStack Router to Solid 2.0.0-beta.16, where every <Link> desynced the
ids of all its following siblings.

createElement now applies the same wrap as transformChildren: dynamic
children holes that can allocate hydration ids evaluate under their own
owner scope. Regression-tested end-to-end in the runtime hydration suite;
the new test fails with the exact sibling-unclaimed symptom when the wrap
is removed.

Co-Authored-By: Claude Fable 5 <[email protected]>

…rops

mergeProps with a function source creates a memo, which consumes a
hydration child id. The ssr generate evaluated mergeProps(...) in
ssrElement's argument position — before the element's own hydration key
was allocated — while the client claims the element via getNextElement
before applying the spread. The element's id shifted by one on the
server, the client re-created it instead of claiming, and later siblings
re-synced — hiding the drift behind a single duplicated element. Hit in
practice as TanStack Router's <title ref={...} {...attrs}> duplicating on
every hydration (the ref forces the compiler into the mergeProps path).

The ssr generate now defers the merge behind a thunk when hydratable,
and ssrElement allocates the hydration key before resolving function
props, matching the client's allocation order. The runtime regression
test fails with the exact unclaimed-element symptom when either half of
the fix is reverted.

Co-Authored-By: Claude Fable 5 <[email protected]>