test: Add 126 tests for Phase 5 plugins + fix 2 source bugs

Tests (5 files, 126 tests, all passing):
- test_agent_memory.py: 22 tests (store, retrieve, delete, routes, tenant isolation)
- test_graph_rag.py: 22 tests (create, traverse BFS, bidirectional, max_hops, cycles, routes)
- test_marketplace.py: 26 tests (fetch, download, verify, install, categories, routes)
- test_agent_subtasks.py: 25 tests (create, wait, cancel, aggregate, list, model)
- test_external_agent_api.py: 31 tests (run, status, stream, auth, rate limit)

Bugfixes:
- graph_rag/models.py: metadata -> meta (SQLAlchemy reserved attribute)
- marketplace/routes.py: fix default parameter validation

app/plugins/builtins/graph_rag/models.py

@@ -47,6 +47,6 @@ class EntityRelationship(Base, TenantMixin, OwnedMixin):
     relationship_type: Mapped[str] = mapped_column(
         String(50), nullable=False, comment="Type of relationship (e.g. 'works_for', 'has_email', 'related_to')"
     )
-    metadata: Mapped[dict[str, Any] | None] = mapped_column(
-        JSONB, nullable=True, default=dict, comment="Arbitrary metadata about the relationship"
+    meta: Mapped[dict[str, Any] | None] = mapped_column(
+        "metadata", JSONB, nullable=True, default=dict, comment="Arbitrary metadata about the relationship"
     )

app/plugins/builtins/graph_rag/provider.py

@@ -40,7 +40,7 @@ class GraphRAGSearchProvider(BaseSearchProvider):
                         coalesce(r.relationship_type, '') || ' ' ||
                         coalesce(r.source_type, '') || ' ' ||
                         coalesce(r.target_type, '') || ' ' ||
-                        coalesce(r.metadata::text, '')
+                        coalesce(r.meta::text, '')
                     ),
                     to_tsquery('pg_catalog.german', :q)
                 ) AS rank
@@ -51,7 +51,7 @@ class GraphRAGSearchProvider(BaseSearchProvider):
                       coalesce(r.relationship_type, '') || ' ' ||
                       coalesce(r.source_type, '') || ' ' ||
                       coalesce(r.target_type, '') || ' ' ||
-                      coalesce(r.metadata::text, '')
+                      coalesce(r.meta::text, '')
                   ) @@ to_tsquery('pg_catalog.german', :q)
                   AND r.id = ANY(:visible_ids)
                 ORDER BY rank DESC
@@ -75,7 +75,7 @@ class GraphRAGSearchProvider(BaseSearchProvider):
                         coalesce(r.relationship_type, '') || ' ' ||
                         coalesce(r.source_type, '') || ' ' ||
                         coalesce(r.target_type, '') || ' ' ||
-                        coalesce(r.metadata::text, '')
+                        coalesce(r.meta::text, '')
                     ),
                     to_tsquery('pg_catalog.german', :q)
                 ) AS rank
@@ -86,7 +86,7 @@ class GraphRAGSearchProvider(BaseSearchProvider):
                       coalesce(r.relationship_type, '') || ' ' ||
                       coalesce(r.source_type, '') || ' ' ||
                       coalesce(r.target_type, '') || ' ' ||
-                      coalesce(r.metadata::text, '')
+                      coalesce(r.meta::text, '')
                   ) @@ to_tsquery('pg_catalog.german', :q)
                 ORDER BY rank DESC
                 LIMIT :lim

app/plugins/builtins/graph_rag/routes.py

@@ -108,7 +108,7 @@ async def list_relationships(
                 "target_type": r.target_type,
                 "target_id": str(r.target_id),
                 "relationship_type": r.relationship_type,
-                "metadata": r.metadata,
+                "metadata": r.meta,
                 "owner_id": str(r.owner_id) if r.owner_id else None,
                 "created_at": r.created_at.isoformat() if r.created_at else None,
             }

app/plugins/builtins/graph_rag/services.py

@@ -61,7 +61,7 @@ async def create_relationship(
         target_type=target_type,
         target_id=target_id,
         relationship_type=relationship_type,
-        metadata=metadata or {},
+        meta=metadata or {},
         owner_id=owner_id,
     )
     db.add(rel)
@@ -75,7 +75,7 @@ async def create_relationship(
         "target_type": rel.target_type,
         "target_id": str(rel.target_id),
         "relationship_type": rel.relationship_type,
-        "metadata": rel.metadata,
+        "metadata": rel.meta,
         "owner_id": str(rel.owner_id) if rel.owner_id else None,
         "created_at": rel.created_at.isoformat() if rel.created_at else None,
     }
@@ -150,7 +150,7 @@ async def traverse_graph(
                 "target_type": rel.target_type,
                 "target_id": str(rel.target_id),
                 "relationship_type": rel.relationship_type,
-                "metadata": rel.metadata,
+                "metadata": rel.meta,
             })
 
             if target_key not in visited:
@@ -186,7 +186,7 @@ async def traverse_graph(
                 "target_type": rel.target_type,
                 "target_id": str(rel.target_id),
                 "relationship_type": rel.relationship_type,
-                "metadata": rel.metadata,
+                "metadata": rel.meta,
             })
 
             if source_key not in visited:

app/plugins/builtins/marketplace/routes.py

@@ -96,7 +96,7 @@ async def get_marketplace_listing(
 @router.post("/install/{name}", response_model=MarketplaceInstallResponse)
 async def install_from_marketplace(
     name: str,
-    body: MarketplaceInstallRequest = MarketplaceInstallRequest(name=""),
+    body: MarketplaceInstallRequest = MarketplaceInstallRequest.model_construct(name=""),
     db: AsyncSession = Depends(get_db),
     current_user: dict = Depends(require_admin),
 ):
@@ -138,7 +138,7 @@ async def install_from_marketplace(
 @router.post("/verify/{name}", response_model=MarketplaceVerifyResponse)
 async def verify_plugin_signature(
     name: str,
-    body: MarketplaceInstallRequest = MarketplaceInstallRequest(name=""),
+    body: MarketplaceInstallRequest = MarketplaceInstallRequest.model_construct(name=""),
     db: AsyncSession = Depends(get_db),
     current_user: dict = Depends(require_permission("marketplace:read")),
 ):