feat(java): add kmp-lsp as an alternative language server (#1891)

docs/java.md

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+# Java language servers
+
+Settings › Languages & Frameworks › Language Servers lists Eclipse JDT Language
+Server (`jdtls`) and [kmp-lsp](https://github.com/Hessesian/kmp-lsp). Select either
+tool and use **Language server for Java** to choose one. The choice can be global
+or limited to the current project. **Automatic** prefers jdtls and falls back to
+kmp-lsp when jdtls is not installed; **None** disables both.
+
+Install kmp-lsp from that page, or point its executable path at an existing
+installation. The IDE downloads a platform distribution containing both kmp-lsp
+and its native JAR indexer. Reinstall and uninstall manage both together.
+
+kmp-lsp offers syntax-based Java code insight without running a JVM. It does not
+provide JDT's compiler analysis, Lombok integration, or JDT-specific refactorings.
+Java Application builds, classpath discovery and the Microsoft Java debugger still
+require jdtls; use jdtls for those flows. Maven and Gradle build tasks can run
+independently of the selected code-insight server.
+
+This built-in choice applies to Java. Kotlin and Swift keep their existing server
+choices. To use another server, add it with **New Language Server**, assign its
+languages, and disable the servers it replaces.