feat(plugin-experiment-react-native): add React Native Experiment plugin

[Mercy811]

Summary

• Add the new @amplitude/plugin-experiment-react-native package at version 1.0.0-beta.0.
• Integrate the Experiment React Native client with Analytics identity and exposure event forwarding.
• Scope Analytics Connector access by instance name for multi-instance support.
• Add unit and integration coverage plus package documentation and build configuration.

Ticket: https://linear.app/amplitude/issue/SDKRN-60/create-react-native-experiment-analytics-plugin-package

Manual test on expo-app example app and see requests to https://flag.lab.amplitude.com/sdk/v2/flags and https://api.lab.amplitude.com/sdk/v2/vardata?v=0 after pressing "START EXPERIMENT" button.

Validation

• Plugin typecheck and lint pass.
• Plugin tests pass: 7 tests.
• Affected Analytics React Native mobile suite passes: 65 tests.

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: No

---

Note

Medium Risk
Touches Analytics identity and event-bridge wiring used by Experiment, including multi-instance connector scoping. The new plugin is additive and covered by unit/integration tests.

Overview
Adds @amplitude/plugin-experiment-react-native so React Native Analytics can initialize Experiment, share identity, and forward exposure events.

The plugin wraps Experiment.initializeWithAmplitudeAnalytics, inherits serverZone/instanceName from Analytics unless overridden, and stops the Experiment client on teardown. The Expo example wires it in with a Start Experiment button.

React Native Analytics now passes instanceName into getAnalyticsConnector, setConnectorUserId, and setConnectorDeviceId so multi-instance apps do not mix Experiment identity or events.

^{Reviewed by Cursor Bugbot for commit d9c5dd8. Configure here.}

[linear-code]

SDKRN-60

SDKW-59

[github-actions]

size-limit report 📦

Path	Size
packages/analytics-browser/lib/scripts/amplitude-min.js.gz	61.54 KB (0%)
packages/session-replay-browser/lib/scripts/session-replay-browser-min.js.gz	134.97 KB (0%)
packages/unified/lib/scripts/amplitude-min.umd.js.gz	215.58 KB (0%)
@amplitude/element-selector (gzipped esm)	2.67 KB (0%)

[Mercy811]

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^{Reviewed by Cursor Bugbot for commit d9c5dd8. Configure here.}

[chatgpt-codex-connector]

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