feat(iios): @mentions via inbox fan-out + my-annotations query (pins/saves)

Mentions ride the existing event-driven inbox — no chat parsing in the kernel:
- send() carries an OPAQUE mentions[] (userIds) into the message event; the kernel
  never parses "@". The app supplies the notify-list.
- InboxProjector fans out a MENTION inbox item (new generic inbox kind) to each
  mentioned *participant* (never the sender), idempotent per source message; reading
  the thread resolves the reader's MENTION + NEEDS_REPLY items to DONE.
- New MENTION value in the generic IiosInboxItemKind taxonomy (migration).

Pins/saves reuse the annotation primitive; new generic query powers a Saved list:
- MessageService.listMyAnnotated(principal, type) + GET /v1/threads/my-annotations
  returns the caller's annotated messages (type "save") with thread context.

Tests: 182 pass (+4: mention fan-out, resolve-on-read, saved query, opaque mentions).
Verified live: mention→inbox delivery, read→resolve, pin/save persistence.

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

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

@@ -191,6 +191,7 @@ export class MessageService {
     idempotencyKey: string,
     traceId: string = randomUUID(),
     parentInteractionId?: string,
+    mentions?: string[],
   ): Promise<MessageDto> {
     const thread = await this.prisma.iiosThread.findUnique({ where: { id: threadId } });
     if (!thread) throw new NotFoundException('thread not found');
@@ -245,7 +246,9 @@ export class MessageService {
           datacontenttype: 'application/json',
           traceparent: `00-${traceId.replace(/-/g, '')}-0000000000000000-01`,
           insignia: { scopeSnapshotId: thread.scopeId, correlationId: traceId, idempotencyKey, dataClass: 'internal' },
-          data: { interactionId: created.id, threadId, senderActorId: actor.id },
+          // `mentions` is an OPAQUE app-supplied notify-list (userIds) — the kernel never parses
+          // "@"; the inbox projector generically fans out a notification to those actors.
+          data: { interactionId: created.id, threadId, senderActorId: actor.id, mentions: mentions ?? [] },
         };
         await tx.iiosOutboxEvent.create({
           data: {
@@ -416,6 +419,48 @@ export class MessageService {
     return { interactionId, threadId: target.threadId, type: annotationType, value, op, users };
   }
 
+  /**
+   * Generic "my annotated interactions" — every message the caller annotated with a given
+   * type, newest first, with thread context. The app uses type "save" for a personal
+   * bookmarks list (and could use "pin" for a cross-thread pinned view). Generic: the kernel
+   * never interprets the type string.
+   */
+  async listMyAnnotated(
+    principal: MessagePrincipal,
+    annotationType: string,
+  ): Promise<Array<{ message: MessageDto; threadId: string; threadSubject: string | null }>> {
+    const scope = await this.actors.findScope(principal);
+    if (!scope) return [];
+    const actor = await this.actors.resolveActor(scope.id, principal);
+    const anns = await this.prisma.iiosInteractionAnnotation.findMany({
+      where: { actorId: actor.id, annotationType },
+      orderBy: { createdAt: 'desc' },
+      select: { targetInteractionId: true },
+    });
+    const ids = anns.map((a) => a.targetInteractionId);
+    if (ids.length === 0) return [];
+    const [interactions, agg] = await Promise.all([
+      this.prisma.iiosInteraction.findMany({
+        where: { id: { in: ids } },
+        include: {
+          parts: { orderBy: { partIndex: 'asc' } },
+          actor: { include: { sourceHandle: true } },
+          thread: { select: { subject: true } },
+        },
+      }),
+      this.annotationsByInteraction(ids),
+    ]);
+    const byId = new Map(interactions.map((i) => [i.id, i]));
+    return ids
+      .map((id) => byId.get(id))
+      .filter((i): i is NonNullable<typeof i> => Boolean(i && i.threadId))
+      .map((i) => ({
+        message: this.toDto(i, i.threadId as string, agg.get(i.id) ?? []),
+        threadId: i.threadId as string,
+        threadSubject: i.thread?.subject ?? null,
+      }));
+  }
+
   // ─── helpers ────────────────────────────────────────────────────
 
   /** Aggregate annotations for the given interactions into { type, value, users[] } groups. */