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/f32io.h

@@ -26,10 +26,11 @@ int  f32_read_root_file_w(const char *name11, u8 **out_data, u32 *out_size);
 int  f32_write_root_file_w(const char *name11, const u8 *data, u32 size);
 int  f32_list_root_w(f32_list_cb_fn emit, void *user_data);
 
-/* 目录列举 / 路径定位 / 长路径读取 */
+/* 目录列举 / 路径定位 / 长路径读取 / 按簇读文件 */
 int  f32_list_dir_w(u32 dir_clus, f32_list_entry_fn emit, void *user_data);
 int  f32_find_path_dir_lfn_w(const char *path, u32 *out_clus);
 int  f32_read_path_lfn_w(const char *path, u8 **out_data, u32 *out_size);
+int  f32_read_file_by_clus_w(u32 clus, u32 size, u8 *out_buf, u32 buf_cap);
 
 /* 流式直读到指定缓冲（绕过 f32_data 4MB 上限，zhfont 字库加载用） */
 int  f32_read_path_lfn_to_w(const char *path, u8 *dst, u32 cap, u32 *out_size);