[codex] Fix async renderer configure race

[raashish1601]

Summary

Fixes #3752.

This caches the in-flight async renderer initialization inside createRoot.configure, so repeated configure calls while a WebGPU-style gl callback is still resolving reuse the same renderer setup instead of invoking gl multiple times. After the shared renderer resolves, configuration rereads current root state before continuing so the latest pending configure can apply the latest size.

A regression test covers two concurrent configure calls with an async gl callback and different sizes, asserting that gl is called once and the final store size comes from the latest configure call.

Validation

• corepack yarn jest packages/fiber/tests/index.test.tsx --runInBand
• corepack yarn prettier --check packages/fiber/src/core/renderer.tsx packages/fiber/tests/index.test.tsx
• corepack yarn eslint packages/fiber/src/core/renderer.tsx packages/fiber/tests/index.test.tsx (passes with existing warning-only repo baseline)
• corepack yarn typecheck
• corepack yarn build
• git diff --check

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