Refactor content helpers and E2E panel utilities

[heznpc]

Summary

• Extract reusable content translation/cache/correction helpers out of the main content script.
• Split panel E2E utilities into a shared helper and add direct helper coverage.
• Keep manifest/script-order and runtime policy tests aligned with the new module boundary.

Validation

• npm run check:all
• npm run test:e2e
• npm run release:preflight