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

programs/include/Api/Syscall.hpp

@@ -167,6 +167,12 @@ namespace Montauk {
     // Block until the mixer state serial differs from the caller's snapshot.
     static constexpr uint64_t SYS_AUDIOWAIT           = 129;
 
+    // Threading
+    static constexpr uint64_t SYS_THREAD_SPAWN        = 130;
+    static constexpr uint64_t SYS_THREAD_EXIT         = 131;
+    static constexpr uint64_t SYS_THREAD_JOIN         = 132;
+    static constexpr uint64_t SYS_THREAD_SELF         = 133;
+
     static constexpr uint32_t CLIPBOARD_MAX_TEXT_BYTES = 256 * 1024;
 
     static constexpr uint32_t IPC_SIGNAL_READABLE    = 1u << 0;