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

userland/lazybox/lazybox.c

@@ -35,6 +35,7 @@
 #include <drivers/hpet.h>
 #include <drivers/nvram.h>
 #include <drivers/lpt.h>
+#include <kernel/ktime.h>
 #include <kernel/sub_lang.h>
 #include <kernel/cpp_kernel.h>
 #include <userland/snake.h>
@@ -718,6 +719,19 @@ static int applet_iodev(int argc, char** argv) {
     return 0;
 }
 
+static int applet_ktime(int argc, char** argv) {
+    (void)argc; (void)argv;
+    uint64_t ns = ktime_ns();
+    printk(ANSI_BRIGHT_CYAN "Monotonic clock (ktime):\n" ANSI_RESET);
+    printk("  Source : %s%s\n", ktime_source(),
+           ktime_is_highres() ? " (nanosecond resolution)" : " (10 ms tick)");
+    printk("  Uptime : %llu.%03llu s (%llu ns)\n",
+           (unsigned long long)(ns / 1000000000ULL),
+           (unsigned long long)((ns / 1000000ULL) % 1000ULL),
+           (unsigned long long)ns);
+    return 0;
+}
+
 static int applet_hpet(int argc, char** argv) {
     (void)argc; (void)argv;
     if (!hpet_available()) {
@@ -2465,6 +2479,7 @@ static const lazybox_applet_t applets[] = {
     {"reg",           applet_reg,           "reg query|add|set|stats",   "NT configuration registry",  "Kernel"},
     {"iodev",         applet_iodev,         "iodev",                     "NT I/O Manager devices & IRP","Kernel"},
     {"hpet",          applet_hpet,          "hpet",                      "High Precision Event Timer",  "Hardware"},
+    {"ktime",         applet_ktime,         "ktime",                     "Monotonic high-res clock",    "Kernel"},
     {"nvram",         applet_nvram,         "nvram",                     "Dump CMOS NVRAM bytes",       "Hardware"},
     {"lpt",           applet_lpt,           "lpt [text]",                "Send text to LPT1 parallel",  "Hardware"},
     {"rand",          applet_rand,          "rand [count]",              "Generate random numbers",    "Crypto"},