feat(channel): 跨平台 IM 接入抽象契约（UnifiedMessage/PlatformAdapter/Capabilities/Actor 身份）

internal/channel/adapter/actor.go

@@ -0,0 +1,71 @@
+package adapter
+
+// Role is the strongly typed identity role the channel layer assigns to a
+// message sender. It is derived from channel-level actor metadata (login state,
+// account binding, group membership) by the strategy engine, never from prompt
+// text. This is a project red line: identity resolution must not rely on
+// natural-language hints.
+type Role string
+
+const (
+	// RoleOwner is the bound owner/primary account.
+	RoleOwner Role = "owner"
+	// RoleMember is a non-owner participant (for example a stranger in a group).
+	RoleMember Role = "member"
+	// RoleSystem is a system/synthetic sender (platform notice, bot).
+	RoleSystem Role = "system"
+	// RoleUnknown is a sender whose identity could not be determined.
+	RoleUnknown Role = "unknown"
+)
+
+// Valid reports whether r is one of the known roles.
+func (r Role) Valid() bool {
+	switch r {
+	case RoleOwner, RoleMember, RoleSystem, RoleUnknown:
+		return true
+	default:
+		return false
+	}
+}
+
+// Actor is the strongly typed identity metadata attached to a message sender.
+// The channel layer derives it from channel telemetry (login session, account
+// binding, group membership) rather than from the message's free-text sender
+// name. Owner detection and group isolation read this field, not prompt text.
+type Actor struct {
+	// Role is the resolved identity role.
+	Role Role
+	// UserID is the stable platform user identifier.
+	UserID string
+	// DisplayName is the human-readable sender name, used for display only.
+	DisplayName string
+	// IsGroup is true when the actor represents a group/room conversation
+	// rather than a single user.
+	IsGroup bool
+	// GroupID is the group identifier, set when IsGroup is true.
+	GroupID string
+	// GroupName is the human-readable group name, used for display only.
+	GroupName string
+}
+
+// IsOwner reports whether the actor is the bound owner account.
+func (a Actor) IsOwner() bool { return a.Role == RoleOwner }
+
+// IsGroupChat reports whether the actor represents a group conversation.
+func (a Actor) IsGroupChat() bool { return a.IsGroup }
+
+// IsSystem reports whether the actor is a system/synthetic sender.
+func (a Actor) IsSystem() bool { return a.Role == RoleSystem }
+
+// IsUnknown reports whether the actor's role could not be determined.
+func (a Actor) IsUnknown() bool { return a.Role == RoleUnknown }
+
+// Resolve is a pure helper that infers IsGroup and the group identity from the
+// GroupID when the channel layer has not set them explicitly, so adapters can
+// populate a minimal Actor and still get correct group flags.
+func (a Actor) Resolve() Actor {
+	if a.GroupID != "" {
+		a.IsGroup = true
+	}
+	return a
+}