The previous commit (f963ae3) used per_item_max_bytes and per_vault_*_max_bytes
which don't match the Rust core's struct (per_item_max_count and
per_vault_*_cap_bytes). Also fixes the per-item semantics: it's a COUNT of
attachments per item, not a byte sum.
Spec and plan docs updated in-place so future Task 7 cap-enforcement
implementation uses the correct names + semantics.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
71c182af9a