feat: add Kotlin/Android error and stacktrace compression

[Cyvid7-Darus10]

This addresses #2 by adding a Kotlin/Android filter to contextzip. I took a look at how the existing filters work (cargo_cmd, go_cmd, error_cmd) and followed the same pattern for Gradle/Kotlin.

The new contextzip gradle command handles three kinds of noise that Android developers deal with constantly. First, Kotlin compiler errors — those e: and w: lines get collected and presented as a numbered summary instead of being buried in build output. Second, Android/JVM stack traces — framework frames from android.*, androidx.*, java.*, kotlin.*, kotlinx.*, dalvik.*, and friends get collapsed into a "(+ N framework frames hidden)" line while your app code stays visible. Third, Gradle task spam — those 30+ "> Task :app:compileSomething" lines that nobody reads get collapsed into a single "(N Gradle tasks executed)" summary. The BUILD SUCCESSFUL/FAILED line is always preserved.

Here is what the before/after looks like for a typical Android build failure:

Before (raw Gradle output):

> Task :app:preBuild UP-TO-DATE
> Task :app:preDebugBuild UP-TO-DATE
> Task :app:compileDebugAidl NO-SOURCE
... 28 more task lines ...
> Task :app:compileDebugKotlin
e: file:///src/App.kt:15:42 Unresolved reference: foo
e: file:///src/Bar.kt:30:10 Type mismatch
> Task :app:compileDebugKotlin FAILED
BUILD FAILED in 12s

After (contextzip gradle build):

Kotlin: 2 errors
1. e: file:///src/App.kt:15:42 Unresolved reference: foo
2. e: file:///src/Bar.kt:30:10 Type mismatch

(31 Gradle tasks executed)
BUILD FAILED in 12s

And for stack traces, a typical Android crash that spits out 15+ framework frames gets compressed to just your app frames plus a hidden count.

The implementation registers contextzip gradle {build,test,lint} as subcommands with passthrough for any other Gradle tasks. I also added .kt/.kts extension mapping to the Java language in filter.rs for code filtering, and added the gradle/gradlew/./gradlew pattern to discover/rules.rs so the hook can automatically rewrite gradle commands. All 1056 existing tests still pass along with the 7 new ones I added.

Closes #2