Pin react peerDependency to the exact synced renderer version

[ram-devv1]

Summary:

Fixes #57079.

react-native@0.85.3 declares "react": "^19.2.3" in peerDependencies, so package managers happily install e.g. react@19.2.6 — but the embedded renderer only supports the exact React version it was synced with (the 0.85.x Paper bundle throws Incompatible React versions unless React.version === "19.2.3", and the Fabric bundle still embeds a pinned version: "19.2.3"). Install succeeds, launch crashes.

This PR pins packages/react-native/package.json peerDependencies.react to the exact synced version (19.2.3, matching the workspace-root dev pin, the helloworld template, and the renderer bundle), restoring the pre-0.76 exact-pin practice (0.74.0 shipped "react": "18.2.0"). A mismatched React now surfaces as an install-time peer warning instead of a runtime crash. It also adds a monorepo consistency test so future React syncs cannot silently reintroduce the drift.

Changelog:

[GENERAL] [FIXED] - Pin react-native peerDependency on react to the exact synced renderer version so installs reject React versions the renderer does not support (fixes #57079)

Test Plan:

• yarn jest scripts/monorepo-tests/__tests__/check-packages-test.js — 6/6 pass, including the new the react-native peer for react must exactly match the synced renderer version test.
• Negative control: temporarily restored ^19.2.3 and re-ran the new test — it fails as expected; re-applied the fix and it passes.
• yarn eslint --max-warnings 0 scripts/monorepo-tests/__tests__/check-packages-test.js — clean.
• prettier --check on both changed files — clean.
• Verified against published tarballs: npm view react-native@0.85.3 peerDependencies shows the old ^19.2.3, and the 0.85.3 tarball's ReactNativeRenderer-dev.js contains the exact 19.2.3 runtime check; semver simulation confirms 19.2.6 satisfies ^19.2.3 but not 19.2.3.
• Could not run: native builds / RNTester bundling (no device toolchain in this environment); change is metadata + a Node-only test, no runtime code touched.

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