Phase 5.5-5.9: Plugin-Marketplace, Agent Memory, GraphRAG, Subagents, External Agent API

5.5 Plugin-Marketplace:
- New plugin: marketplace/ (models, routes, services, schemas, config)
- MarketplaceListing model (global, no tenant_id)
- Ed25519 signature verification via PluginSignature
- Endpoints: list, detail, install, verify, categories
- Config: MARKETPLACE_SERVER_URL setting

5.6 Agent Memory (persistent):
- New plugin: agent_memory/ (models, routes, services, schemas)
- AgentMemory model with embedding vector(768) + HNSW index
- store_memory() with auto-embedding
- retrieve_relevant_memories() with pgvector cosine similarity
- Semantic search endpoint

5.7 GraphRAG:
- New plugin: graph_rag/ (models, routes, services, provider, schemas)
- EntityRelationship model (source/target type+id, relationship_type, metadata)
- BFS graph traversal (bidirectional, configurable depth)
- GraphRAGSearchProvider registered in unified_search

5.8 Subagents / Multi-Agent:
- AgentCoordinator class (create_subtask, wait_for_subtask, aggregate, cancel)
- AgentSubtask model + migration 0002_agent_subtasks.sql
- 6 new API endpoints for subtask management
- Tools registered in AI tool registry

5.9 External Agent API:
- external_api.py: POST /run, GET /status, POST /stream (SSE)
- Bearer API token authentication
- Rate limiting: 10 req/min per token
- ExternalAgentRequest/Response schemas

3 new plugins registered in main.py and __init__.py
All files py_compile clean

app/plugins/builtins/automation/plugin.py

@@ -57,7 +57,7 @@ class AutomationPlugin(BasePlugin):
             "mail.received",
             "workflow.timeout",
         ],
-        migrations=["0001_initial.sql"],
+        migrations=["0001_initial.sql", "0002_agent_subtasks.sql"],
         permissions=[
             "automation:read",
             "automation:write",
@@ -185,6 +185,12 @@ class AutomationPlugin(BasePlugin):
             register_agent_comm_tool()
         except Exception:
             logger.exception("Failed to register agent communication tool")
+        # Register agent coordinator tools
+        try:
+            from app.plugins.builtins.automation.agent_coordinator import register_agent_coordinator_tools
+            register_agent_coordinator_tools()
+        except Exception:
+            logger.exception("Failed to register agent coordinator tools")
         # Register MiniApps from manifest
         try:
             from app.plugins.builtins.kommunikation.contracts import MiniAppRegistry
@@ -222,6 +228,12 @@ class AutomationPlugin(BasePlugin):
             unregister_agent_comm_tool()
         except Exception:
             logger.exception("Failed to unregister agent communication tool")
+        # Unregister agent coordinator tools
+        try:
+            from app.plugins.builtins.automation.agent_coordinator import unregister_agent_coordinator_tools
+            unregister_agent_coordinator_tools()
+        except Exception:
+            logger.exception("Failed to unregister agent coordinator tools")
         # Unregister MiniApps
         try:
             from app.plugins.builtins.kommunikation.contracts import MiniAppRegistry