Require invalid_type_pack for schema-level upgrade_from violations

[callumalpass]

05A already says an invalid pack manifest is invalid_type_pack, but no fixture checked a manifest that fails the type-pack schema itself. mdbase-rs returns the raw schema code there (schema_one_of for upgrade_from: []); mdbase-ts returns invalid_type_pack.

• 05A names two more invalid cases explicitly: an empty upgrade_from list, and a baseline without digest or document.
• Two fixtures, seed-upgrade-invalid-empty-baselines and seed-upgrade-invalid-incomplete-baseline, with example packs.

check_v03_tests.py passes, and removing upgrade_from from the empty example makes the fixture fail. mdbase-ts passes both fixtures unchanged. mdbase-rs fails both until its companion fix lands.