Align to firmware PR #247 (merged): cap OFFBAND_CAP_BLOCK=0x02, FIRMWARE_VER_CODE
15, 0xC2 CMD_OFFBAND_BLOCK (ADD/REMOVE/LIST/CLEAR), MAX_BLOCKED_KEYS=32, BLOCK_LIST
streamed-dump framing (0xFF count / index / 0xFE end) + APP_START early-END.
Switch sync model to union / always-retain-local (app-local never wiped; portable
across Offband clients, local-only on non-Offband). Global (by-pubkey) app store.
Fold in channel all-matching-pubkeys rule, dual name-key index sourcing (0x8A vs
0x80), promote-and-prune age-out, gaps G1/L1/L2/L3, interop invariant.
Feature #164 / Epic A #165 / Epic B #166; firmware doc #244.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>