Adds 4 regression tests:
- vite.config.ts entry modules must exist as source files
- content.js must NOT use inline script injection (textContent)
- interceptors.js must be a standalone IIFE file
- manifest.json content_scripts must reference content.js
Prevents future build-breaking phantom entry point errors
(the probeFn.js/scrapeFn.js issue kfj001 hit).
