docs(tests): clarify entry migration and renderer contract coverage

tests/headless/renderers.test.mjs

@@ -20,6 +20,7 @@ test('renderer catalog captures exact version/structure mappings without React v
 });
 // 组装仅在同一个 render 实现时共享别名包装；拒绝空 renderer、ID 冲突与模型契约不符，getter 只读取一次并保留 memo 对象。
 test('React assembly preserves aliases only for the same component and rejects invalid renderers or model contracts',()=>{
+ // render 返回 null，仅用作可比较的组件身份；此例检查包装与别名缓存，没有执行实际节点 UI。
  const render=()=>null,assembly=createReactRenderers([{...descriptor,render}],registry);assert.equal(assembly.nodeTypes.meter.type,render);assert.ok(Object.isFrozen(assembly.nodeTypes));assert.equal(assembly.edgeTypes.meter,undefined);
  assert.throws(()=>createReactRenderers([{...descriptor,render:null}]),/invalid_react_renderer/);assert.throws(()=>createReactRenderers([{...descriptor,render},{...descriptor,componentId:'other',render:()=>null}]),/renderer_id_conflict/);assert.throws(()=>createReactRenderers([{...descriptor,dataVersion:2,render}],registry),/renderer_model_mismatch/);
  let reads=0;const getter=createReactRenderers([{...descriptor,get render(){reads++;return render;}}]);assert.equal(reads,1);assert.equal(getter.definitions[0].render,render);assert.equal(getter.nodeTypes.meter,assembly.nodeTypes.meter);
@@ -29,6 +30,7 @@ test('React assembly preserves aliases only for the same component and rejects i
 test('installed node and edge renderers receive original records and transforms while absent schemas still fall back',()=>{
  const customEdge=defineComponent({id:'plugin:edge',dataVersion:1,structure:'connection',validate:()=>true,features:[]}),r=createRegistry([...builtinComponents(),definition,customEdge]),other={...node,id:'second',geometry:{...node.geometry,x:300}},edge={id:'edge',incarnation:1,structure:'connection',componentId:'plugin:edge',dataVersion:1,ownerCanvasId:'root',source:{elementId:'meter',portId:'custom-out'},target:{elementId:'second',portId:'custom-in'},path:{type:'custom',retained:true},data:{path:{own:true},metric:99}},source=createDocument('project',[{id:'root',parent:null}],[node,other,edge]),catalog=createRendererCatalog([...builtinRendererDefinitions,descriptor,{...descriptor,componentId:'plugin:edge',structure:'connection',rendererId:'meter-edge'}]),p=projectCanvas(source,'root',r,new Set(),()=>undefined,null,catalog);
  assert.equal(p.nodes[0].type,'meter');assert.equal(p.nodes[0].data.__headlessFallback,undefined);assert.equal(p.nodes[0].data.__headlessRecord,source.elements.get('meter'));assert.deepEqual(p.nodes[0].data.__headlessRecord.data.title,{opaque:true});assert.equal(p.nodes[0].data.__headlessTransform.scale,1);assert.equal(p.edges[0].type,'meter-edge');assert.equal(p.edges[0].data.__headlessRecord,source.elements.get('edge'));assert.deepEqual(p.edges[0].data.__headlessRecord.path,{type:'custom',retained:true});
+ // 已知模型但未装 renderer 与未来数据版本都走占位；前面的可信 __headlessRecord 必须覆盖用户同名字段。
  const missing=projectCanvas(source,'root',r,new Set(),()=>undefined);assert.equal(missing.nodes[0].type,'unsupported');assert.equal(missing.edges[0].type,'unsupported');const future=createDocument('project',[{id:'root',parent:null}],[{...node,dataVersion:2}]);assert.equal(projectCanvas(future,'root',r,new Set(),()=>undefined,null,catalog).nodes[0].type,'unsupported');
 });
 // 加载前预览必须显式提供 preview，实现与正式 renderer 独立捕获；非法 preview 或不一致别名被拒绝。