fix: fixed packaging

[gitsad]

What does this PR do?

Fixes a package-distribution bug that made three published packages unresolvable in React Native / Metro bundlers that don't opt into package exports resolution — notably Metro/Snackager (Expo Snack), which failed with Failed to resolve dependency … (Can't resolve '').

@mobile-reality/mdma-spec, @mobile-reality/mdma-runtime, and @mobile-reality/mdma-renderer-react-native previously exposed only an exports map (import + types), with no main/module/react-native entry fields. Bundlers that resolve the classic main/react-native fields (Metro without unstable_enablePackageExports, Snackager) found no entry point.

This adds main, module, and react-native fields (and a default export condition) alongside the existing exports — fully additive and backwards-compatible. Bundlers that read exports are unaffected; those that read main/react-native now resolve a valid entry. Side benefit: consumers no longer need unstable_enablePackageExports in their Metro config to use these packages.

Closes #

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing behavior to change)
• Refactor (no functional change)
• Documentation
• CI / tooling

Packages Affected

• @mobile-reality/mdma-spec
• @mobile-reality/mdma-runtime
• @mobile-reality/mdma-renderer-react-native (not in the list above; patch bump)

Checklist

• I have read the CONTRIBUTING guide.
• My code follows the existing code style (pnpm format and pnpm lint pass).
• I have added or updated tests that cover my changes. (N/A — package-metadata change only; no runtime code changed.)
• All tests pass (pnpm test).
• Type-checking passes (pnpm typecheck). (Repo-wide: 22/22 packages.)
• I have added a changeset (pnpm changeset) if this change affects published packages. (patch × 3.)
• New or changed MDMA schemas are backwards-compatible (or marked as breaking). (No schema changes.)
• Sensitive fields are marked with sensitive: true where appropriate. (N/A.)