fix: use browser field object map instead of exports for webpack compatibility

[NorOldBurden]

Summary

Fixes @constructive-io/fetch@1.0.0 breaking webpack builds for browser targets. The package uses require('node:http') and require('node:https') for *.localhost DNS routing in Node.js. Although wrapped in a runtime guard (process.versions?.node), webpack statically analyzes all require() calls and cannot resolve node: URIs for browser targets.

Approach: Split browser-safe entry points (localhost-fetch.browser.ts, index.browser.ts) that only use globalThis.fetch, and use the browser field object map in package.json to tell bundlers to swap node-specific files for their browser counterparts.

This follows the constructive-pnpm standard which explicitly says never use the exports map — the browser field object form achieves the same goal without that complexity:

\"browser\": {
  \"./index.js\": \"./index.browser.js\",
  \"./esm/index.js\": \"./esm/index.browser.js\",
  \"./localhost-fetch.js\": \"./localhost-fetch.browser.js\",
  \"./esm/localhost-fetch.js\": \"./esm/localhost-fetch.browser.js\"
}

This is well-supported by webpack, browserify, rollup, vite, esbuild, and parcel.

Review & Testing Checklist for Human

• Verify @constructive-io/graphql-query and @constructive-io/upload-client webpack builds succeed with this version
• Check that Node.js consumers still get the node:http/node:https localhost routing (the main/module entry points are unchanged)
• Confirm no node: scheme references in the built browser files (dist/index.browser.js, dist/esm/index.browser.js)

Notes

• The previous version of this PR used an exports field which is an anti-pattern per constructive-pnpm standards. Replaced with browser field object form which is simpler and equally effective.
• Version bumped to 1.1.0 (from original PR commit).
• Browser entry points just bind globalThis.fetch — no localhost workaround needed since browsers resolve *.localhost natively.

Link to Devin session: https://app.devin.ai/sessions/af68f5f456bb4faa9e937563ef2a5eb0
Requested by: @pyramation