revisão e complementação da documentação do projeto

docs/adr/ADR-006-no-token-passthrough.en-us.md

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+# ADR-006: Prohibition of token passthrough
+
+**Status:** Accepted.
+**Source:** this ADR is the canonical record of this decision. For implementation and validation context, see `RI/docs/AS-BUILT.md` and, where applicable, the relevant contract in `RI/docs/interfaces/`.
+
+## Context
+
+Can the agent's token be forwarded to the backend?
+
+## Decision
+
+No — blind token passthrough is prohibited; inbound ≠ outbound identity.
+
+## Alternatives Considered
+
+Direct passthrough of the client's token.
+
+## Consequences
+
+EP-07 implements exchange/service account per backend.