feat(gui,kernel): 1080p HD desktop, polished chrome, ktime clock + live FPS

GUI polish / HD:
- Default display mode raised to 1920x1080 (video=1920x1080); make run/vnc use
  vgamem_mb=64 and -m 512M. The growable heap absorbs the larger backbuffer,
  shadow and wallpaper (observed: one 16 MB growth to a 48 MB heap).
- Wallpaper: three-stop vertical gradient, a soft concentric-frame edge vignette
  for depth, a finer faint grid, and a centred brand mark.
- Window chrome: brighter/saturated titlebar gradient when focused, an accent
  underline on the active window, and larger/softer drop shadows.
- Default session windows are placed and sized for the HD work area.
- Live FPS pill in the taskbar tray (green/amber/red by rate); tray widened so
  FPS + CPU trace + memory badge + clock no longer overlap.

Kernel:
- kernel/time/ktime.c + include/kernel/ktime.h (new): a unified monotonic
  high-resolution clock that prefers the HPET (nanosecond) and falls back to the
  100 Hz PIT tick. Wired ktime_init() into boot; drives the compositor's FPS
  sampling. New `ktime` LazyBox applet reports the source and uptime.

Verified live (screenshotted): boots to 1920x1080, KTIME reports
"source: HPET, nanosecond resolution", the polished desktop renders with the
active-window accent and vignette, and the tray shows a live FPS reading.
Clean build on x86_64/aarch64/armv8i; 0 panics / 0 OOM.

Co-Authored-By: Claude Opus 4.8 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Fh5z6V7nGPbHvqVG5p4CXX

kernel/main.c

@@ -76,6 +76,7 @@
 #include <drivers/hpet.h>
 #include <drivers/nvram.h>
 #include <drivers/lpt.h>
+#include <kernel/ktime.h>
 #include <drivers/virtio_input.h>
 #include <gui/gui.h>
 #include <init/init.h>
@@ -135,6 +136,7 @@ static void subos_modular_core_boot(void) {
     nvram_init();
     lpt_init();
 #endif
+    ktime_init();
     canvas_init();
     pty_init();
     virtio_rng_init();
@@ -330,7 +332,7 @@ void kernel_main(void* memory_map, uint64_t memory_map_count) {
     printk(ANSI_BRIGHT_CYAN "   SUB-OS 64-Bit [%s] Modular Monolithic Kernel %s\n" ANSI_RESET, arch_get_name(), kernel_get_version());
     printk(ANSI_BRIGHT_CYAN "=================================================================\n\n" ANSI_RESET);
 
-    init_early("root=/dev/sda console=tty1 init=/bin/lazybox video=1280x720 quiet");
+    init_early("root=/dev/sda console=tty1 init=/bin/lazybox video=1920x1080 quiet");
     rtc_init();
 
     printk(KERN_INFO "[1/14] Initializing 64-Bit GDT, IDT, PIC & PIT Timer... ");