Port from qwibitai/nanoclaw#1962: modern Signal V2-only groups surface on
dataMessage.groupV2.id, not groupInfo.groupId. signal-cli versions differ
in which field they expose for V2 groups — some forward the underlying
libsignal envelope verbatim (groupV2), others normalize everything into
groupInfo. Without a groupV2 read, V2-only groups appear as DMs because
groupInfo is undefined and the adapter misroutes them to the sender's
DM session.
Reads groupV2.id first, falls back to groupInfo.groupId. Also hardens
chat_name extraction against non-dict groupInfo payloads (crashed with
AttributeError under malformed envelopes).
6 new tests cover V2 routing, V1 legacy compatibility, V2-preferred
precedence, no-group DM path, allowlist enforcement, and malformed
payloads.
6c2406c5e1