test(exports): assert every exports subpath resolves to a source file that exists

[YevheniiKotyrlo]

Summary

#451 corrected the two ./components/* source targets #445 reported, which is what this PR fixed when I opened it. The manifest change is gone. What stays is a guard main does not have: src/__tests__/package/exports-source-targets.test.ts walks the exports map the way node does (an exact key first, then the pattern whose literal prefix before * is longest) and asserts every source and react-native target names a file on disk. Export conditions match on key presence rather than target existence, so a wrong target is a hard MODULE_NOT_FOUND with no fallthrough to import or require.

Two censuses drive it: every literal subpath, and every module in src/components/ reduced to the subpath a consumer would import. A case asserts both are non-empty, so a narrowed map cannot quietly produce zero cases.

Tests

All 37 pass on main. On f70c402, before #451, it fails exactly ./components/copyComponentProperties and ./components/index and passes the other 33.

Verification

On Windows with Node 26:

• yarn lint clean
• yarn typecheck clean
• yarn build clean
• yarn test --maxWorkers=2 --coverage: every failure also fails on main on this machine (the four babel cases)
• node --test node/__tests__/*.mjs: the same 11 assertions fail on main on this machine

Base

Re-written on main (a5002c5) as the test alone.

[YevheniiKotyrlo]

No device frame

This PR adds a test only, and what it checks is module resolution, which happens before anything renders.