feat: filesystem and Files app support for >64 file entries, 64-bit sizes, async ops, GUI toolkit improvements to devexplorer app

kernel/src/Api/Syscall.hpp

@@ -255,6 +255,9 @@ namespace Montauk {
     /* Power.hpp -- cross-process graceful power-off request channel */
     static constexpr uint64_t SYS_POWER_REQUEST       = 135;
 
+    /* Filesystem.hpp -- paginated directory read (path, names, max, startIndex) */
+    static constexpr uint64_t SYS_READDIR_AT          = 136;
+
     // Graceful power-off request actions (SYS_POWER_REQUEST). The desktop posts
     // a pending action and exits; login.elf reads it, runs the shutdown stages,
     // then issues the matching SYS_SHUTDOWN / SYS_RESET.