feat(orchestrator): add MS23 per-agent message history and SSE stream endpoints

GET /agents/:id/messages - paginated message history
GET /agents/:id/messages/stream - SSE live stream with replay

Partial #693

apps/orchestrator/Dockerfile

@@ -21,7 +21,8 @@ FROM base AS deps
 COPY packages/shared/package.json ./packages/shared/
 COPY packages/config/package.json ./packages/config/
 COPY apps/orchestrator/package.json ./apps/orchestrator/
-# Copy API prisma schema so prisma generate can run in the orchestrator build
+# Copy API package.json + prisma schema so prisma generate can find the project root
+COPY apps/api/package.json ./apps/api/package.json
 COPY apps/api/prisma ./apps/api/prisma
 
 # Copy npm configuration for native binary architecture hints
@@ -48,7 +49,8 @@ COPY --from=deps /app/packages/shared/node_modules ./packages/shared/node_module
 COPY --from=deps /app/packages/config/node_modules ./packages/config/node_modules
 COPY --from=deps /app/apps/orchestrator/node_modules ./apps/orchestrator/node_modules
 
-# Copy API prisma schema and generate the Prisma client for the orchestrator
+# Copy API package.json + prisma schema so Prisma can find the project root
+COPY apps/api/package.json ./apps/api/package.json
 COPY apps/api/prisma ./apps/api/prisma
 RUN pnpm --filter=@mosaic/orchestrator prisma:generate