Prepare v13 package for release

[dtroupe-plaid]

Summary

• Excludes generated/local package artifacts while keeping v13 build output and native SDK files in the npm package.
• Adds CHANGELOG.md with v13.0.0 release notes and ports all V12.* entries from master, excluding V11/V10 history.
• Restores package sanity coverage with npm pack entrypoint checks in CI.
• Aligns iOS fallback onExit payloads with the RN callback contract and extends contract coverage.
• Restores the MIT license and trims stale README setup wording.

Tarball comparison

• v13.0.0 local pack: 6,537,959 bytes (6.24 MiB) packed, 30,978,639 bytes (29.54 MiB) unpacked, 92 files.
• v12.8.3 npm pack: 110,797 bytes (108.20 KiB) packed, 379,660 bytes (370.76 KiB) unpacked, 102 files.
• v13 is larger primarily because it ships the bundled iOS LinkKit.xcframework.
• Confirmed v13 tarball includes build/** and excludes dist/, coverage/, and example/**.

Validation

• npm run lint
• npm test -- --coverage --no-watch --passWithNoTests
• npm run build
• npm run check:package
• cd example && npx expo prebuild --platform android --clean
• cd example/android && ./gradlew testDebugUnitTest

[github-actions]

Coverage after merging codex/v13-release-readiness into develop-v13 will be

100.00%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
ReactNativePlaidLinkSdkModule.ts	100%	100%	100%	100%
index.ts	100%	100%	100%	100%