Notice only covers SessionUpdate variants the agent-client-protocol
dependency already decodes but the projection doesn't special-case.
SessionUpdate is an internally-tagged enum with no unknown-variant
fallback, so a genuinely new wire variant fails deserialization before
the projection ever sees it, rather than becoming a Notice. A new
variant needs the dependency upgraded first.
Adds a projection test asserting that an unrecognised sessionUpdate
tag is a deserialization error.
Refs #186
Miguel Palhas
b225fbdd69