fix(signals): require complete store seeds

[GabbeV]

Summary

Split from #3194 to isolate the seed type-safety change.

Derived store APIs currently accept a Partial<T> seed while exposing both the returned store and the projection draft as a complete T. This allows required properties to be absent at runtime even though reads and mutations are typed as if they are present.

This changes the seed to a complete T for createStore(fn, seed), createProjection, and createOptimisticStore(fn, seed) across the signals, client, and server declarations. It also applies the existing NoFn<T> exclusion consistently, since a callable root cannot be distinguished from the function form by the runtime dispatch.

Existing tests that intentionally initialize from {} and establish the complete value through mutation now use {} as any. This preserves that pattern as an explicit unsafe escape hatch rather than claiming it is type-safe.

No runtime behavior is intended to change.

How did you test this change?

• Ran pnpm types in packages/signals.
• Ran pnpm exec tsc -p tsconfig.build.json --noEmit in packages/solid.
• Compiled store.type-tests.ts independently with strict TypeScript settings.
• Ran the focused projection, store type, and server async tests: 184 tests passed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5ceea76

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

This PR includes changesets to release 11 packages

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

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[codspeed-hq]

Merging this PR will not alter performance

✅ 136 untouched benchmarks

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_{Comparing GabbeV:fix/require-complete-store-seeds (5ceea76) with next (ff96a67)}