ADR 0593 §6: a composition read from composed-<node> is a record never
applied, and the engine applies only what it composes itself, so no
composition carries a signature and nothing is verified. The agent's
trusted signers, its signed-composition test and the unused signing
helper of the integration bed go, so mesh-sdk can drop SignComposed,
VerifyComposed and Composed.Signature.
Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL
jschoubben
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