feat(unified-react-native): add unified-react-native support

[Mercy811]

Summary

• Add the new @amplitude/unified-react-native beta package.
• Initialize Analytics, Experiment, Session Replay, and Guides and Surveys through initAll.
• Share serverZone, instanceName, and translated logLevel defaults while allowing blade-specific overrides.
• Expose Experiment, Session Replay, and Guides and Surveys accessors alongside the React Native Analytics API.
• Ship a React Native CLI autolinking preset so applications directly install only the unified package.
• Add a bare React Native example that consumes the one-package preset and exercises every blade.
• Add package documentation, build configuration, and full unit coverage.

Stacked on #1944, which provides @amplitude/plugin-experiment-react-native.

Local test with the example app examples/unified/react-native-app. Able to see requests from all blades.

Testing

• pnpm install --frozen-lockfile
• Unified React Native build, typecheck, lint, and tests (18 tests, 100% coverage)
• Unified example lint and typecheck
• React Native CLI config resolves all five transitive native dependencies for iOS and Android
• Android :app:generateAutolinkingPackageList
• iOS pod install (five native modules plus Engagement and AsyncStorage codegen)
• Production iOS Metro bundle
• pnpm docs:check
• pnpm lint
• pnpm lint:deps
• pnpm test (30 projects)
• pnpm build — the new package and its dependencies build successfully, but the repository-wide command stalls in the unrelated @amplitude/segment-session-replay-plugin Rollup task
• pnpm test:examples — the base branch references a missing root jest.setup.examples.js

Checklist

• PR title follows the conventional commit format
• Breaking change: No

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Note

Medium Risk
New beta SDK orchestrates multi-blade init and native autolinking for customer apps; behavior is well-tested but affects integration surfaces (RN ≥0.76, New Architecture for Engagement).

Overview
Introduces @amplitude/unified-react-native (1.0.0-beta.0) as a single install that bundles Analytics, Experiment, Session Replay, and Guides and Surveys. A new init() path initializes Analytics, registers blade plugins, starts Experiment, and boots Engagement, with shared serverZone, instanceName, and logLevel defaults and per-blade overrides. Initialization is idempotent; failed init can retry after removing partially added blades.

The package ships react-native.config.js, an autolinking preset that exposes five transitive native modules (analytics, experiment, engagement, session replay, AsyncStorage) so apps only depend on the unified package. Public API re-exports Analytics helpers plus experiment() / sessionReplay() accessors, AmpMaskView, and a library enrichment plugin for event metadata.

Adds a bare React Native 0.76 example under examples/unified/react-native-app that loads the preset, enables Android New Architecture, dedupes Metro resolution for pnpm workspaces, and demonstrates manual init() via a button (API key from root .env). Includes unit tests for the client factory, autolinking preset, and library plugin.

^{Reviewed by Cursor Bugbot for commit 8358dca. Configure here.}