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/schemas.py

@@ -0,0 +1,59 @@
+"""Pydantic schemas for the GraphRAG plugin."""
+
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Any
+
+from pydantic import BaseModel, Field
+
+
+class RelationshipCreate(BaseModel):
+    source_type: str = Field(..., max_length=50, description="Entity type of the source (e.g. 'contact', 'company')")
+    source_id: str = Field(..., description="UUID of the source entity")
+    target_type: str = Field(..., max_length=50, description="Entity type of the target (e.g. 'email', 'task')")
+    target_id: str = Field(..., description="UUID of the target entity")
+    relationship_type: str = Field(..., max_length=50, description="Type of relationship (e.g. 'works_for', 'has_email')")
+    metadata: dict[str, Any] | None = Field(None, description="Arbitrary metadata about the relationship")
+
+
+class RelationshipRead(BaseModel):
+    id: str
+    source_type: str
+    source_id: str
+    target_type: str
+    target_id: str
+    relationship_type: str
+    metadata: dict[str, Any] | None = None
+    owner_id: str | None = None
+    created_at: datetime | None = None
+
+
+class TraverseRequest(BaseModel):
+    source_type: str = Field(..., max_length=50, description="Entity type of the starting node")
+    source_id: str = Field(..., description="UUID of the starting node")
+    max_hops: int = Field(3, ge=1, le=10, description="Maximum traversal depth")
+    relationship_types: list[str] | None = Field(None, description="Optional filter by relationship types")
+
+
+class GraphNode(BaseModel):
+    entity_type: str
+    entity_id: str
+    depth: int
+    path: list[str] = []
+
+
+class GraphEdge(BaseModel):
+    source_type: str
+    source_id: str
+    target_type: str
+    target_id: str
+    relationship_type: str
+    metadata: dict[str, Any] | None = None
+
+
+class TraverseResponse(BaseModel):
+    nodes: list[GraphNode]
+    edges: list[GraphEdge]
+    total_nodes: int
+    total_edges: int