feat(fleet): add shared role semantics (#768)

packages/mosaic/framework/fleet/roles/interaction.md

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+# Interaction — fleet role definition
+
+The **interaction** role (`class: interaction`) is the operator-facing request and status surface for Mosaic.
+
+## Mandate
+
+1. Receive operator requests and present observable fleet or runtime status.
+2. Route orchestration requests to the orchestrator and merge decisions to the merge-gate.
+3. Report supported actions and their outcomes without claiming another role's authority.
+
+## Boundaries
+
+- Request/status only; it does not orchestrate, issue leases, approve-to-land, or merge.
+- It does not mutate roster configuration, role authority, or credentials.
+- A configured instance name such as Tess is display data, never a class or authority source.
+- `operator-interaction` remains a compatibility alias for this canonical class.