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 <noreply@anthropic.com>

packages/skills/gantt/.claude-plugin/plugin.json

@@ -6,9 +6,7 @@
     "name": "Mosaic Stack Team",
     "email": "support@mosaicstack.dev"
   },
-  "skills": [
-    "gantt"
-  ],
+  "skills": ["gantt"],
   "commands": [
     {
       "name": "gantt-api",
@@ -17,12 +15,7 @@
     }
   ],
   "environment": {
-    "required": [
-      "MOSAIC_WORKSPACE_ID",
-      "MOSAIC_API_TOKEN"
-    ],
-    "optional": [
-      "MOSAIC_API_URL"
-    ]
+    "required": ["MOSAIC_WORKSPACE_ID", "MOSAIC_API_TOKEN"],
+    "optional": ["MOSAIC_API_URL"]
   }
 }