feat: FS-E strict filesystem mode - ext4 rw driver, FAT32 big-disk fix, forced re-login

- CODE/dsk/ext4.c: minimal full ext4 read/write (GPT probe, feature gate,
  extent depth 0/1 rw, block/inode alloc-free, dir insert, write-verify);
  boot selftest PASS on p2. Unsupported features panic (FS-E2x), zero fallback.
- DSK fat32 write: on-demand FAT entry RMW + chunked free-cluster scan
  (fixes "no free clusters" on 5.3G ESP); rec_len shrink offset (+4) and
  chunk alignment fixes. USER.CONF write-verify ok, firstInit flip ok.
- First-boot: wizard -> persist -> forced login (FS-E06 if skipped/failed)
  -> desktop. login.elf loaded via system/user/use fallback.
- FirstInit network page: Connect now panics NET-E01 (no wlan stack);
  Save (config only) is the only path forward.
- FirstInit/DSK fatal: ohMyLogo lotus fatal screen (NET-E01 / FS-E series).
- Boot screen: Logo.png image removed, "DESHAB P01" text centered only;
  dcp/xj logos regenerated from TEXTURES/.
- run_qemu.bat: main GPT image on SATA ide.0 (AHCI provider must see ext4).

CODE/linux/pack_system_image.sh

@@ -174,7 +174,11 @@ if [[ "$esp_bytes" -ge $((4096 * 1024 * 1024)) ]]; then
 fi
 
 mkfs.vfat -F 32 -n DESHABBOOT -s "$fat_cluster_sectors" "$p1" >/dev/null
-mkfs.ext4 -F -q -L DESHAB -U "$EXT4_UUID" -m 1 "$p2"
+# DSK 内嵌 ext4 读写驱动支持范围：4K block / 256B inode / extent 树，
+# 不支持 journal、metadata_csum、64bit（遇到即 panic FS-E28）——
+# 因此这里必须显式关闭这三个 feature。
+mkfs.ext4 -F -q -L DESHAB -U "$EXT4_UUID" -m 1 \
+    -b 4096 -I 256 -O ^has_journal,^metadata_csum,^64bit,^resize_inode "$p2"
 echo "[pack] filesystems:"
 blkid "$p1" "$p2" || true