[DO NOT MERGE] feat(core): add opt-in assertion instrumentation - #6592

String(symbol) throws a TypeError and crashes the assertion reporter when runtime values contains a Symbol.

SENTRY_SDK_PATH_MARKERS uses forward-slash literals, but Metro/Babel filename may contain backslashes on Windows, causing the plugin to instrument the SDK's own files and inject a self-referential require('@sentry/react-native').

Identifiers bound inside nested function expressions (e.g., arrow-function parameters) are collected and then referenced in the emitted values object at the assertion call site, where they are out of scope and throw a ReferenceError at runtime.

The assertion Babel plugin rewrites const { assert } = console; assert(false) with rethrow: true, turning a report-only console.assert into a throwing assertion that crashes after capturing.

Wrap String(value) in a try-catch so a throwing toString or [Symbol.toPrimitive] doesn't break the reporting path and cause double-capture.

SENTRY_SDK_PATH_MARKERS uses forward-slash literals, but Metro/Babel filename may contain backslashes on Windows, causing the plugin to fail to skip Sentry's own files and risking a self-referential require('@sentry/react-native') if any assertion pragma exists in SDK source.

Also found at:

• packages/core/src/js/tools/sentryAssertionBabelPlugin.ts:197

Identifiers bound inside nested functions (e.g. arrow-function parameters) are collected and then referenced in the emitted values object at the assertion call site, where they are out of scope and cause a ReferenceError at runtime.

The guard if (values !== undefined) allows null to reach flattenValues, where Object.keys(null) throws a TypeError. Change the check to if (values != null) to safely reject both null and undefined.