Support .kts files in the default tag importer

[redcatbear]

Situation

OpenFastTrace currently supports kt files in the default tag importer, but not kts files.

That means coverage tags placed in Kotlin script files such as build.gradle.kts or settings.gradle.kts are not picked up unless users add extra importer configuration.

Expected Behavior

OpenFastTrace should support .kts files in the default tag importer, alongside .kt.

Motivation

Kotlin DSL build files are common in Gradle-based projects. They are a natural place for OFT coverage tags in build logic and build-related implementation artifacts.

Without default .kts support, users can easily assume those files are traced when they are not.

Suggested Change

Add kts to the default supported extensions in the tag importer.

Evidence

In the current OFT release line, the default supported extensions include kt, but not kts.