docs(tess): add migration evidence set

docs/tess/M5-MIGRATION-ROLLBACK.md

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+# TESS-MIG-001 — Rollback Procedure
+
+Rollback is configuration/binding reversal, not a database rollback: no Hermes schema migration or automatic data import is implemented by the landed adapter.
+
+1. Stop sending new traffic to the Mosaic Hermes adapter by reverting the external runtime/channel binding through its authorized deployment process.
+2. Keep the gateway registration and core contracts unchanged unless a reviewed code rollback is required; `AgentRuntimeProviderRegistry` registration is explicit and non-replacing (`packages/agent/src/runtime-provider-registry.ts`).
+3. Do not replay an unsupported Kanban, skills, memory, tools, or cron operation. The transitional matrix is intentionally fail-closed.
+4. Preserve Mosaic audit, session, and operator-memory records under their normal scoped retention rules; do not copy them into Hermes as a rollback shortcut.
+5. For an in-flight coordination request, use the owned handoff observation/result flow in `MosCoordinationService`; do not create a second orchestrator path.
+6. Capture the binding reversal, affected scope, correlation IDs, and reason in the approved operational record before retrying a cutover.