fix(resolve): fall back to module entry when browser entry is non-ESM in build

[semimikoh]

… in build

Summary

• Packages like roughjs@4.5.2 have browser pointing to an IIFE bundle and module pointing to ESM, with no exports field
• Rolldown's native resolver picks the browser entry first, which has no ESM exports → MISSING_EXPORT error
• Vite's tryResolveBrowserEntry already has a heuristic (hasESMSyntax check) to fall back to module when browser is non-ESM, but it
  wasn't being used during Rolldown builds
• Added a pre-resolve plugin in oxcResolvePlugin that intercepts these cases and routes through Vite's resolver

Test plan

• Added unit test verifying non-ESM browser entry falls back to module entry
• Verify with reproduction from MISSING EXPORT #22285 (@visactor/vrender-kits → roughjs@4.5.2)

Fixes #22285

[sapphi-red]

Thanks for the PR, but this is an expected behavior: #22285 (comment)