feat(iios): message senderName + dev user directory

- Messages now carry senderName (resolved actorId → sourceHandle.externalId) so
  clients render usernames instead of raw actor cuids.
- GET /v1/dev/users exposes the dev directory (DEV_USERS keys) so a host app can
  validate add-by-username; real apps validate against their user store / MDM.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/src/messaging/message.service.ts

@@ -13,6 +13,7 @@ export interface MessageDto {
   id: string;
   threadId: string;
   senderActorId: string;
+  senderName: string;
   content: string;
   contentRef?: string;
   parentInteractionId?: string;
@@ -198,7 +199,7 @@ export class MessageService {
     // Idempotency: a repeat key returns the existing message (no re-increment).
     const existing = await this.prisma.iiosInteraction.findUnique({
       where: { scopeId_idempotencyKey: { scopeId: thread.scopeId, idempotencyKey } },
-      include: { parts: { orderBy: { partIndex: 'asc' } } },
+      include: { parts: { orderBy: { partIndex: 'asc' } }, actor: { include: { sourceHandle: true } } },
     });
     if (existing) return this.toDto(existing, threadId);
 
@@ -260,7 +261,7 @@ export class MessageService {
 
         return tx.iiosInteraction.findUniqueOrThrow({
           where: { id: created.id },
-          include: { parts: { orderBy: { partIndex: 'asc' } } },
+          include: { parts: { orderBy: { partIndex: 'asc' } }, actor: { include: { sourceHandle: true } } },
         });
       });
 
@@ -269,7 +270,7 @@ export class MessageService {
       if (err instanceof Prisma.PrismaClientKnownRequestError && err.code === 'P2002') {
         const winner = await this.prisma.iiosInteraction.findUniqueOrThrow({
           where: { scopeId_idempotencyKey: { scopeId: thread.scopeId, idempotencyKey } },
-          include: { parts: { orderBy: { partIndex: 'asc' } } },
+          include: { parts: { orderBy: { partIndex: 'asc' } }, actor: { include: { sourceHandle: true } } },
         });
         return this.toDto(winner, threadId);
       }
@@ -341,7 +342,7 @@ export class MessageService {
   async getMessageById(id: string, principal?: MessagePrincipal): Promise<MessageDto | null> {
     const i = await this.prisma.iiosInteraction.findUnique({
       where: { id },
-      include: { parts: { orderBy: { partIndex: 'asc' } } },
+      include: { parts: { orderBy: { partIndex: 'asc' } }, actor: { include: { sourceHandle: true } } },
     });
     if (!i || !i.threadId) return null;
     if (principal) await this.actors.assertOwns(principal, i.scopeId); // tenant fence (KG-02) when called on behalf of a caller
@@ -352,7 +353,7 @@ export class MessageService {
     const interactions = await this.prisma.iiosInteraction.findMany({
       where: { threadId },
       orderBy: { occurredAt: 'asc' },
-      include: { parts: { orderBy: { partIndex: 'asc' } } },
+      include: { parts: { orderBy: { partIndex: 'asc' } }, actor: { include: { sourceHandle: true } } },
     });
     return interactions.map((i) => this.toDto(i, threadId));
   }
@@ -360,7 +361,15 @@ export class MessageService {
   // ─── helpers ────────────────────────────────────────────────────
 
   private toDto(
-    interaction: { id: string; actorId: string | null; parentInteractionId?: string | null; traceId: string | null; occurredAt: Date; parts: Array<{ kind: string; bodyText: string | null; contentRef: string | null }> },
+    interaction: {
+      id: string;
+      actorId: string | null;
+      actor?: { displayName: string | null; sourceHandle: { externalId: string } | null } | null;
+      parentInteractionId?: string | null;
+      traceId: string | null;
+      occurredAt: Date;
+      parts: Array<{ kind: string; bodyText: string | null; contentRef: string | null }>;
+    },
     threadId: string,
   ): MessageDto {
     const text = interaction.parts.find((p) => p.kind === 'TEXT');
@@ -369,6 +378,7 @@ export class MessageService {
       id: interaction.id,
       threadId,
       senderActorId: interaction.actorId ?? '',
+      senderName: interaction.actor?.sourceHandle?.externalId ?? interaction.actor?.displayName ?? 'unknown',
       content: text?.bodyText ?? '',
       contentRef: file?.contentRef ?? undefined,
       parentInteractionId: interaction.parentInteractionId ?? undefined,