fix(reactive): make createSelector transition-aware

[birkskyum]

This is an Opus 5 solution, to this solid 1 bug that was reported in the solid-start repo

• [Bug?]: createSelector doesn't work with hydration solid-start#2114

Problem

createSelector does not update its subscribers when the source changes inside a transition. The subscribed computation is silently skipped, so a <Show> or classList driven by the selector never re-renders, even though a createEffect reading the same selector fires with the correct value.

The most common way to hit this is @solidjs/router: every navigation (including setSearchParams) is wrapped in startTransition, and startTransition only creates a Transition when Scheduler || SuspenseContext is set. So any app with a <Suspense> boundary and a router-driven selector is affected. SolidStart's default template ships exactly that shape, which is why it tends to surface as "my selector broke when I added SSR".

Fixes #2940. Very likely the same underlying cause as #666.

Cause

Inside a transition, Solid tracks staleness on tState, not state. writeSignal handles this:

if (!TransitionRunning) o.state = STALE;
else o.tState = STALE;

[changeset-bot]

🦋 Changeset detected

Latest commit: 0b0d724

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

This PR includes changesets to release 2 packages

Name	Type
solid-js	Patch
test-integration	Patch

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