fix(rules): route Kotlin script files to Kotlin review rules (#1091)

* fix(rules): route Kotlin script files to Kotlin review rules

* fix(allowlist): exclude Kotlin script tests by default

Extend the default Kotlin test-path exclusion to `.kts` and add focused extension and exclusion regression coverage.

Validated on the #1091 branch with `make check`, `make test`, `make coverage`, and the required OCR self-review.

Co-authored-by: wu21-web <wu2196674@icloud.com>

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Co-authored-by: Tao Xin <wu2196674@icloud.com>