feat: add threading to Scheduler, fix desktop background selection freeze issue

kernel/src/Api/Process.hpp

@@ -98,6 +98,8 @@ namespace Montauk {
         for (int i = 0; i < Sched::MaxProcesses && count < maxCount; i++) {
             auto* proc = Sched::GetProcessSlot(i);
             if (!proc || proc->state == Sched::ProcessState::Free) continue;
+            // Skip sibling-thread slots; only show one entry per process.
+            if (proc->primarySlot != i) continue;
 
             buf[count].pid = (int32_t)proc->pid;
             buf[count].parentPid = (int32_t)proc->parentPid;
@@ -154,6 +156,25 @@ namespace Montauk {
         return i;
     }
 
+    // ====================================================================
+    // Threading
+    // ====================================================================
+    static int Sys_ThreadSpawn(uint64_t entry, uint64_t arg, uint64_t userStackTop) {
+        return Sched::SpawnThread(entry, arg, userStackTop);
+    }
+
+    [[noreturn]] static void Sys_ThreadExit(int exitCode) {
+        Sched::ExitCurrentThread(exitCode);
+    }
+
+    static int Sys_ThreadJoin(int tid, int* outExitCode) {
+        return Sched::JoinThread(tid, outExitCode);
+    }
+
+    static int Sys_ThreadSelf() {
+        return Sched::GetCurrentTid();
+    }
+
     static int Sys_Chdir(const char* path) {
         auto* proc = Sched::GetCurrentProcessPtr();
         if (proc == nullptr || path == nullptr) return -1;