add react-native export condition resolving to browser build

[davor-bauk-sh]

Problem

Follow-up to #397 / #399 and react/metro#1681.

Metro resolves package exports with the conditions import/require plus react-native. It never sets browser or node, so for lru-cache it falls through to default, i.e. dist/esm/index.min.js, which does import('node:diagnostics_channel').

Current Metro does recognise the .catch()-guarded dynamic import as optional at build time (the fix from metro#1681), so bundling succeeds. On native, though, the runtime require of an unresolved optional module reports a fatal error through ErrorUtils.reportFatalError instead of throwing, so the promise .catch() never sees it and the app crashes on startup. This is not the node condition being loaded by mistake; it is the default entry.

Change

Add a react-native condition to the root export, in both tshy.exports and the generated exports, pointing at the existing browser build (dist/{esm,commonjs}/browser/). No new build output, no source change. react-native is the conventional condition packages use to give Metro a dedicated entry, and every other resolver ignores it.

Verified with a bare-specifier probe against this branch after npm run prepare:

[node <default>]
  require -> dist/commonjs/node/index.min.js
  import  -> dist/esm/node/index.min.js
[node --conditions=react-native]
  require -> dist/commonjs/browser/index.min.js
  import  -> dist/esm/browser/index.min.js
[node --conditions=browser]
  require -> dist/commonjs/browser/index.min.js
  import  -> dist/esm/browser/index.min.js

tshy preserves the condition on rebuild (git status clean apart from this diff). Browser builds contain no node: references.

Not touched: the ./raw export, which is generated by tshy from source. React Native users importing lru-cache/raw would still hit the default build; happy to hand-write that export too if you'd prefer.

🤖 Generated with Claude Code