Verdict: BLOCKING — do not merge as-is. The slice-4 importer join-typing opener
(EnumOverUnderlyingFamily) is unsound: it changes program semantics and marks the
result Full fidelity.
Reviewers: GPT-5.5 and Gemini 3.1 Pro (both non-Claude per the AGENTS.md roster),
each in an isolated worktree. They independently found the same root cause via different
fixtures. All findings below were reproduced by the requester on clean base vs branch
checkouts using DecompilerHarness --dump.