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/UTSM/include/utsm/idt.h

@@ -58,4 +58,12 @@ void idt_irq_eoi(u8 vector);
 typedef int (*idt_exception_hook_t)(u64 vector, u64 error_code, u64 rip);
 void idt_set_exception_hook(idt_exception_hook_t hook);
 
+/* P1（万物互联）: PIC IMR 位操作 —— kern.irq.unmask/mask 总线服务后端。
+ * 仅 ISA IRQ 0-15（越界 → IRQ-E01 panic 零降级）；
+ * unmask IRQ8-15 自动放开主片 IRQ2 级联。
+ * apic_route=1 时 PIC 已全屏蔽（IOAPIC 接管），本操作无效果——该路径的
+ * 解屏蔽随 P6 真 IRQ 输入走 IOAPIC 接线。 */
+void pic_irq_unmask(u8 irq);
+void pic_irq_mask(u8 irq);
+
 #endif