feat(panic): FUCK [panic] mode=strict|fallback + realtest image variant

- UTSM panic_full returns in fallback mode (logs [PANIC:FALLBACK] + code + hit
  count); panic_halt keeps always-halt sites (CPU exception, VMM-E11 LA57,
  VMM-E15 DSK jump, UTSM-E42 test hook). Call sites given safe continuations.
- Mode passed to DSK/FirstInit/login/desktop via DSK_BOOT_FLAG_PANIC_FALLBACK;
  DKM kernel_api.panic / kern.log.panic return to driver; ext4 fatal aborts the
  op via setjmp/longjmp and DSK falls back to FAT32 ESP.
- build.ps1/Makefile: dev=strict, release=fallback, new realtest (release
  options + strict); default -Variant all; serialized iso packing under -j.
- Fix '*/' inside comments (dkm.h, kernel_api.h, bus.c) that broke the build.
- Includes pending work: dkm_bus service bus, mt7920/wlan drivers, desktop
  files/startmenu/prank, pe-tools, diskinfo, docs.

Co-authored-by: Cursor <cursoragent@cursor.com>

CODE/desktop/shell.c

@@ -478,6 +478,12 @@ int handle_key(u8 sc) {
     if (sc == 0xB8) { g_alt = 0; return 0; }
     if (sc & 0x80) { g_e0 = 0; return 0; }   /* 其他释放码忽略 */
 
+    /* M3 开始菜单（模态：Esc 关闭 / 搜索输入 / Enter 启动） */
+    if (g_sm_open) return startmenu_key(sc, g_shift);
+
+    /* 快速设置卡片（Esc 收起） */
+    if (g_qs_open && sc == 0x01) { g_qs_open = 0; return 1; }
+
     /* WiFi 快捷卡片（模态：Esc 收起 / 密码模式接管输入） */
     if (g_wifi_open) return wifi_key(sc, g_shift);