refactor: add integrationTest() helper to reduce test boilerplate (#3711)

## Summary
- Adds an `integrationTest()` wrapper in
`packages/fresh/src/test_utils.ts` that calls `Deno.test` with
`sanitizeOps: false` and `sanitizeResources: false`
- Converts ~88 integration tests across 5 files to use the new helper,
removing repetitive sanitizer boilerplate
- Net reduction of ~344 lines (-1678/+1334)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju