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

@@ -47,11 +47,14 @@ 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
 
-# apps/orchestrator/prisma/schema.prisma is a symlink → ../../api/prisma/schema.prisma
-# Docker COPY follows symlinks, so the schema file is already present after
-# "COPY apps/orchestrator ./apps/orchestrator" above.
-# pnpm turbo build runs prisma:generate first (which uses --schema=./prisma/schema.prisma)
-# from within the orchestrator package — no cross-package project-root issues.
+# The repo has apps/orchestrator/prisma/schema.prisma as a symlink for CI use.
+# Kaniko resolves destination symlinks on COPY, which fails because the symlink
+# target (../../api/prisma/schema.prisma) doesn't exist in the container.
+# Fix: remove the dangling symlink first, then copy the real schema file there.
+RUN rm -f apps/orchestrator/prisma/schema.prisma
+COPY apps/api/prisma/schema.prisma ./apps/orchestrator/prisma/schema.prisma
+# pnpm turbo build runs prisma:generate (--schema=./prisma/schema.prisma) from the
+# orchestrator package context — no cross-package project-root issues.
 
 # Build the orchestrator app using TurboRepo
 RUN pnpm turbo build --filter=@mosaic/orchestrator