Fixed probe cleanup

- Offline probes share bounded directory rescans after concurrent file creation
- Cleanup preserves other I/O failures
- Symlink targets remain untouched
- Probe tests use Mockito to reproduce cleanup races and failure boundaries

probe/build.gradle

@@ -17,6 +17,7 @@ dependencies {
     implementation(project(':core'))
     compileOnly(libs.spigot)
     testImplementation('junit:junit:4.13.2')
+    testImplementation('org.mockito:mockito-core:5.23.0')
     testImplementation(libs.gson)
     testImplementation(testFixtures(project(':core')))
     testImplementation('com.github.VolmitSoftware.VolmLib:volmlib-shared:master-SNAPSHOT') {