Kotlin LS spawns heavy zombie processes

[MischaPanch]

See discussion in #1079 for details.

I think we should just always kill the gradle process when shutting down, unless it has some downsides I am missing.

@opcode81 @mareurs @cx-alberto-simoes

[mareurs]

Fix submitted in #1082.

Root cause

KLS triggers Gradle during project indexing, which spawns persistent GradleDaemon processes. These daemons:

• Detach from KLS (reparented to init/systemd) — invisible to psutil.Process.children(recursive=True)
• Use KLS's bundled JRE (JAVA_HOME → ~/.serena/language_servers/static/KotlinLanguageServer/...)
• Have a 3-hour default idle timeout
• Consume ~500MB RSS each

Fix

Override stop() in KotlinLanguageServer to find and terminate Gradle daemons after normal KLS shutdown. We identify them by matching cmdline[0] (the java binary path) against JAVA_HOME/bin/java from this KLS instance's dependency provider.

This ensures we only kill daemons spawned by this KLS instance (matching the bundled JRE path), not unrelated Gradle daemons on the system.

Verified

Controlled before/after test: zero new Gradle daemons left after pytest -m kotlin with the fix (previously 1 new ~500MB daemon per test run).