fix: emit native injection code as CommonJS

[shin4141]

Summary

• emit native injection code with CommonJS require() calls
• preserve CSS side-effect loading and StyleCollection.inject behavior
• add a regression that parses and executes the generated source in script mode

The synthetic module previously retained raw import / export syntax, which reaches Hermes unchanged when Expo's optimize-graph tree shaking is enabled.

Validation

• focused regression: 1 test passed
• full test suite: 56 suites passed (4 skipped), 1,052 tests passed (21 skipped)
• yarn lint
• yarn typecheck
• yarn build
• git diff --check

The exact Expo optimize-graph + Hermes export was not rerun locally; the regression directly covers the script-mode parse failure and the required module/injection behavior.

Closes #414.

AI assistance was used to inspect the issue, implement the focused change, and run validation. I reviewed the complete diff.