feat(#93): implement agent spawn via federation

Implements FED-010: Agent Spawn via Federation feature that enables
spawning and managing Claude agents on remote federated Mosaic Stack
instances via COMMAND message type.

Features:
- Federation agent command types (spawn, status, kill)
- FederationAgentService for handling agent operations
- Integration with orchestrator's agent spawner/lifecycle services
- API endpoints for spawning, querying status, and killing agents
- Full command routing through federation COMMAND infrastructure
- Comprehensive test coverage (12/12 tests passing)

Architecture:
- Hub → Spoke: Spawn agents on remote instances
- Command flow: FederationController → FederationAgentService →
  CommandService → Remote Orchestrator
- Response handling: Remote orchestrator returns agent status/results
- Security: Connection validation, signature verification

Files created:
- apps/api/src/federation/types/federation-agent.types.ts
- apps/api/src/federation/federation-agent.service.ts
- apps/api/src/federation/federation-agent.service.spec.ts

Files modified:
- apps/api/src/federation/command.service.ts (agent command routing)
- apps/api/src/federation/federation.controller.ts (agent endpoints)
- apps/api/src/federation/federation.module.ts (service registration)
- apps/orchestrator/src/api/agents/agents.controller.ts (status endpoint)
- apps/orchestrator/src/api/agents/agents.module.ts (lifecycle integration)

Testing:
- 12/12 tests passing for FederationAgentService
- All command service tests passing
- TypeScript compilation successful
- Linting passed

Refs #93

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

apps/api/src/federation/federation.module.ts

@@ -24,6 +24,7 @@ import { IdentityResolutionService } from "./identity-resolution.service";
 import { QueryService } from "./query.service";
 import { CommandService } from "./command.service";
 import { EventService } from "./event.service";
+import { FederationAgentService } from "./federation-agent.service";
 import { PrismaModule } from "../prisma/prisma.module";
 
 @Module({
@@ -55,6 +56,7 @@ import { PrismaModule } from "../prisma/prisma.module";
     QueryService,
     CommandService,
     EventService,
+    FederationAgentService,
   ],
   exports: [
     FederationService,
@@ -67,6 +69,7 @@ import { PrismaModule } from "../prisma/prisma.module";
     QueryService,
     CommandService,
     EventService,
+    FederationAgentService,
   ],
 })
 export class FederationModule {}