test: the dispatch generators skip FRAD's NLPID map and ICMP's type registries #2560

From the 2026-11-01 conventions audit, re-verified on 73add05a3. test-coverage.rst, "Adding a Protocol, Option or Dumper": a __proto__ registration needs its PINNED_TARGETS entry in examples/generators/dispatch.py, and a new registry adds a Family to FAMILIES; coverage is enumerated from the registries (see "Round-Trip Invariants").

• FRAD.__proto__ (in pcapkit/protocols/link/frad.py: NLPID 0xCC -> IPv4, 0x8E -> IPv6) has no Family in dispatch.py, so test_every_case_has_a_pinned_target never sees it; grep -in frad examples/generators/dispatch.py prints nothing. IPX.__proto__ and Netlink.__proto__ are empty, so nothing is lost there.
• ICMPv4.__type__ (pcapkit/protocols/internet/icmpv4.py) and ICMPv6.__type__ (pcapkit/protocols/internet/icmpv6.py) are type-code -> method maps with register_type, the shape of the mh-message and httpv2-frame families, but examples/generators/options.py FAMILIES has no ICMP entry (grep -in icmp prints nothing). Their round trips use a hand-picked table (__tier__ = 'ALL'), so a type code registered later gets no case.

Fix: FRAD: add a Family and PINNED_TARGETS entries to dispatch.py, and update the totals asserted in test_cases_cover_every_table_named_in_the_issue. ICMP: add ICMPv4 and ICMPv6 type families to options.py.
Blocked: #2542 and #2544 edit dispatch.py (#2544 also options.py), and #2527 reworks FRAD's registration; unblocks when all three merge.