Fix stale mappings for primitive store arrays

[brenelz]

Fixes <For> / mapArray updates when a derived store replaces a same-length array of primitive values.

When store reconciliation updated primitive array entries, it set the per-index signals but did not mark the array as changed. As a result, $TRACK subscribers such as mapArray could keep stale row mappings when the array length stayed the same.

This marks primitive item replacements as array changes so the list mapping reruns correctly.

Added a regression test covering a derived store returning a flat string array.

Fixes #2720.

[changeset-bot]

🦋 Changeset detected

Latest commit: 23c9563

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
@solidjs/signals	Patch
test-integration	Patch
solid-js	Patch
babel-preset-solid	Patch
@solidjs/web	Patch
@solidjs/html	Patch
@solidjs/h	Patch
@solidjs/universal	Patch
@solidjs/element	Patch

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[codspeed-hq]

Merging this PR will not alter performance

✅ 118 untouched benchmarks

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_{Comparing brenelz:fix-store-primitive-array-map (23c9563) with next (99d829e)}