feat: add cwd tracking to kernel, remove shell hack, update system utilities to use getcwd, fix tcc libc stub, fix nonexistent directory issue

kernel/src/Sched/Scheduler.hpp

@@ -44,6 +44,7 @@ namespace Sched {
         uint64_t heapNext;        // Simple bump allocator for user heap
         char args[256];           // Command-line arguments (set by parent via Spawn)
         char user[32];            // Owner user name (inherited from parent on spawn)
+        char cwd[256];            // Absolute current working directory
 
         int runningOnCpu;         // CPU index running this process (-1 if not running)
         bool killPending = false; // Set by Sys_Kill when target is running on another CPU