docs: Misc tree cleanups (#23088)

## Description

Cleanup a few test and docs things in tree.

packages/dds/tree/src/simple-tree/objectNode.ts

@@ -47,7 +47,7 @@ import { TreeNodeValid, type MostDerivedData } from "./treeNodeValid.js";
 import { getUnhydratedContext } from "./createContext.js";
 
 /**
- * Helper used to produce types for object nodes.
+ * Generates the properties for an ObjectNode from its field schema object.
  * @system @public
  */
 export type ObjectFromSchemaRecord<T extends RestrictiveStringRecord<ImplicitFieldSchema>> = {

packages/dds/tree/src/simple-tree/objectNodeTypes.ts

@@ -58,7 +58,9 @@ export interface ObjectNodeSchemaInternalData {
 }
 
 export const ObjectNodeSchema = {
-	// instanceof-based narrowing support for Javascript and TypeScript 5.3 or newer.
+	/**
+	 * instanceof-based narrowing support for ObjectNodeSchema in Javascript and TypeScript 5.3 or newer.
+	 */
 	[Symbol.hasInstance](value: TreeNodeSchema): value is ObjectNodeSchema {
 		return isObjectNodeSchema(value);
 	},

packages/dds/tree/src/test/shared-tree-core/sharedTreeCore.spec.ts

@@ -294,9 +294,9 @@ describe("SharedTreeCore", () => {
 		});
 
 		const sf = new SchemaFactory("0x4a6 repro");
-		const TestNode = sf.objectRecursive("test node", {
+		class TestNode extends sf.objectRecursive("test node", {
 			child: sf.optionalRecursive([() => TestNode, sf.number]),
-		});
+		}) {}
 
 		const tree2 = await factory.load(
 			dataStoreRuntime2,

packages/dds/tree/src/test/simple-tree/api/schemaFactory.examples.spec.ts

@@ -110,7 +110,7 @@ describe("Class based end to end example", () => {
 	});
 
 	// Confirm that the alternative syntax for initialTree from the example above actually works.
-	it("using a mix of insertible content and nodes", () => {
+	it("using a mix of insertable content and nodes", () => {
 		const factory = new TreeFactory({});
 		const theTree = factory.create(
 			new MockFluidDataStoreRuntime({ idCompressor: createIdCompressor() }),