fix(react-native): report correct agent version and fix RN 0.72 init crash

[KishanPRao]

Summary

Reports carried a hardcoded 0.0.1 agent version, and RN 0.72 apps crashed at SDK init because Metro 0.76.9 mis-indexes a babel helper require in sdk-core's bundle.

Changes

• packages/react-native/src/BacktraceClient.ts: read agentVersion from the package version instead of the hardcoded 0.0.1.
• packages/sdk-core/tsconfig.build.json: target ES5 with downlevelIteration so the shipped bundle has no class syntax for the consumer's Metro to transpile into babel helper requires.
• packages/sdk-core/rollup.config.mjs: bundle tslib so the ES5 output is self-contained.

Note

• agentVersion reads package.json through the react-native/src entry Metro uses, so it is correct at runtime; the lib/ builds resolve the path one level too deep, but RN never loads lib/.
• RN 0.72 on Xcode 26 also needs an app-side Podfile snippet for Yoga's -Werror (client side, not SDK); ES5 costs sdk-core ~8KB gzip across all JS SDKs.
• Validated RN 0.72-0.83 (both architectures); unit tests across sdk-core/react-native/browser/react/node.

ref: BT-7354, BT-7406

[melekr]

we're pinning "react-native": ">=0.72.0"