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/graph_rag/plugin.py

@@ -0,0 +1,58 @@
+"""GraphRAG plugin — entity relationship graph with BFS traversal and search provider."""
+
+from __future__ import annotations
+
+from app.plugins.base import BasePlugin
+from app.plugins.manifest import PluginManifest, PluginRouteDef
+
+
+class GraphRAGPlugin(BasePlugin):
+    """GraphRAG plugin for entity relationship graph with BFS traversal."""
+
+    manifest = PluginManifest(
+        name="graph_rag",
+        version="1.0.0",
+        display_name="GraphRAG",
+        description="Entity relationship graph with BFS traversal and unified search integration. Stores typed relationships between entities for knowledge graph exploration.",
+        dependencies=["unified_search"],
+        routes=[
+            PluginRouteDef(
+                path="/api/v1/graph",
+                module="app.plugins.builtins.graph_rag.routes",
+                router_attr="router",
+            ),
+        ],
+        events=[],
+        migrations=["0001_initial.sql"],
+        permissions=[
+            "graph:read",
+            "graph:write",
+        ],
+        is_core=True,
+        author="LeoCRM Team",
+        min_app_version="1.0.0",
+        contract_version="1.0.0",
+    )
+
+    async def on_activate(self, db, service_container, event_bus) -> None:
+        """Activate plugin: register GraphRAG search provider."""
+        from app.plugins.builtins.graph_rag.provider import GraphRAGSearchProvider
+        from app.plugins.builtins.unified_search.provider_registry import get_search_registry
+
+        registry = get_search_registry()
+        try:
+            registry.register(GraphRAGSearchProvider())
+        except Exception:
+            import logging
+            logging.getLogger(__name__).exception("Failed to register GraphRAGSearchProvider")
+
+        await super().on_activate(db, service_container, event_bus)
+
+    async def on_deactivate(self, db, service_container, event_bus) -> None:
+        """Deactivate plugin: unregister search provider and contract."""
+        from app.plugins.builtins.unified_search.provider_registry import get_search_registry
+        get_search_registry().unregister("graph_relationship")
+
+        from app.plugins.builtins.contracts import get_contract_registry
+        get_contract_registry().unregister(self.manifest.name)
+        await super().on_deactivate(db, service_container, event_bus)