Feature parity: port remaining go-RCP tooling packages (iso21434, certgap, formal, codegen)

[SoundMatt]

Background

Feature-equivalence audit against the reference implementation go-RCP (2026-06-19). cpp-RCP matches 39/44 go-RCP packages (+ adds cli/adapt/relay). safety is covered by command_latency_test.cpp. Four go-RCP packages have no cpp-RCP equivalent:

go-RCP pkg	Purpose	Public API
iso21434	Cybersecurity engineering (ISO/SAE 21434)	ComputeRisk, ThreatScenario, TARA, GoalRegistry
certgap	ASIL gap analysis	Registry, GapReport, StandardASILDGaps
formal	In-library LTL verification helpers	Always/Eventually/Until, Checker
codegen	Zone-manifest → controller stub + fusa-req skeleton generator	ParseManifest, Generate

Decision needed

All four are safety/cyber tooling, not RCP transport features. cpp-RCP currently delegates this role to the external cpp-FuSa (cpfusa) tool (gap reports, TARA, traceability) and to TLA+ specs in tla/. So the question is architectural, not just effort:

• Option A — port them as C++ library modules for strict go-RCP API parity.
• Option B — declare them intentionally out of scope for cpp-RCP (tooling lives in cpp-FuSa) and document the divergence.

iso21434 is the most relevant to cpp-RCP's cyber-requirement story and the most self-contained; codegen is the largest. Tracking for a later decision. See companion issue on SoundMatt/go-RCP.