feat: introduce theme management and performance improvements (#7)

internal/collector/collector_test_helpers_linux.go

@@ -0,0 +1,18 @@
+//go:build linux
+
+package collector
+
+// clearUserCache clears the user lookup cache for testing
+func clearUserCache() {
+	userCache.Lock()
+	userCache.m = make(map[int]string)
+	userCache.Unlock()
+}
+
+// userCacheSize returns the number of cached user entries
+func userCacheSize() int {
+	userCache.RLock()
+	defer userCache.RUnlock()
+	return len(userCache.m)
+}
+