fix(knowledge): stop listing workspace knowledge bases on stale creator identity (#6454)

GET /api/knowledge without a workspaceId ORed on knowledge_base.user_id with no
permission check, so a user removed from a workspace kept seeing metadata for every
KB they created there. Scope the creator fallback to legacy KBs with no workspaceId,
matching the workspace-filtered branch and the detail path.

packages/testing/src/mocks/database.mock.ts

@@ -29,6 +29,8 @@ export function createMockSql() {
       toSQL: () => ({ sql: strings.join('?'), params: values }),
       /** Mirrors drizzle's `sql``…`.as(alias)` for aliased select expressions. */
       as: (alias: string) => ({ ...fragment, alias }),
+      /** Mirrors drizzle's `sql``…`.mapWith(decoder)` for typed select expressions. */
+      mapWith: (decoder: unknown) => ({ ...fragment, decoder }),
     }
     return fragment
   }