feat(lsp): add Kotlin Language Server support

[amondnet]

Summary

Add Kotlin Language Server support to packages/lsp using the official JetBrains Kotlin LSP.

Requirements

• Use JetBrains official Kotlin LSP (https://download-cdn.jetbrains.com/kotlin-lsp/)
• Auto-download JRE 21 from vscode-java releases
• Platform support: win-x64, linux-x64, linux-arm64, osx-x64, osx-arm64
• File extensions: .kt, .kts
• Root detection: build.gradle.kts, build.gradle, settings.gradle.kts, settings.gradle, pom.xml

Tasks

• T001 [P] Add platform detection utility function
• T002 [P] Add download/extract utility functions
• T003 Add KotlinServer definition with auto-download
• T004 Export KotlinServer from index.ts
• T005 Add LSP_SERVERS array entry
• T006 Add tests for KotlinServer

References

• Serena SolidLSP implementation: ref/serena/src/solidlsp/language_servers/kotlin_language_server.py
• multispy reference: ref/multispy/src/multilspy/language_servers/kotlin_language_server/

Dependencies

None

Acceptance Criteria

• Kotlin LSP server auto-downloads on first use
• Works on all supported platforms
• Provides diagnostics for .kt and .kts files
• Follows existing server patterns in the codebase