dosforge v0.9.56

Highlights

PCDOS3 + COMPAQ3 now support FAT16 partitions up to 32 MiB
(historical correction).
- Prior dosforge versions restricted IBM PC-DOS 3.00 and the
  Microsoft MS-DOS 3.00 Compaq OEM build to FAT12-only with a
  16 MiB cap, citing "FAT16 was added in PC-DOS 3.10."
- That comment was historically inaccurate. FAT16 was
  introduced in PC-DOS 3.0 (August 1984), and its FORMAT.COM
  already picks FAT12 for partitions <=16 MiB and FAT16 for
  16-32 MiB partitions automatically. Compaq's OEM MS-DOS 3.00
  shipped the same Microsoft kernel and FORMAT.
- You can now build:
  - dosforge create --boot-mode pcdos3 --format fat16 --size 32M
  - dosforge create --boot-mode compaq3 --format fat16 --size 32M
- FAT12 (<=16 MiB) is still the default and remains
  1984-authentic for small XT-IDE drives.
- 32 MiB is the 1984 partition-table addressing cap; >32 MiB
  still requires compaq331 (FAT16B) or msdos5 / msdos622.

Stale _BOOT_MODE_MEDIA_RULES comments + _validate_create_request
messages now describe the correct PC-DOS 3.0 FORMAT.COM behavior.

tests/test_size_cap_snap.py splits PCDOS3 + COMPAQ3 cap tests
into FAT12 (16 MiB) + FAT16 (32 MiB) variants. The
TestFormDiskCapParity drift-prevention test continues to
enforce that every formlogic._BOOT_MODE_MEDIA_RULES max_mb
has a matching disk-side cap branch.

pcdos3 + FAT16 + 32M + IDE -> 33,546,752-byte VHD with
MBR partition type 0x04 (FAT16 <32MiB), COMMAND.COM dated
1984-08-14.
compaq3 + FAT16 + 32M + IDE -> same.
Regression: pcdos3 + FAT12 + 16M + XT-IDE still snaps to
(306, 4, 26) = 15.54 MiB.
Over-cap rejection: pcdos3 + FAT16 + 64M -> ValidationError
with the corrected guidance.