docs(tests): explain input ownership and incremental query assertions

tests/headless/pointer-capture.test.mjs

@@ -6,5 +6,6 @@ import {test} from 'node:test';import assert from 'node:assert/strict';
 import {ownsPointerCapture,acquirePointerCapture,releasePointerCapture} from '../../src/lib/canvas-bindings/pointer-capture.ts';
 // move/up/cancel 检查 pointerId；lostpointercapture 还检查事件 target 与当前捕获状态，空 owner 不匹配。
 test('pointer move/up/cancel only match their owner and old lost-capture cannot cancel a replacement target',()=>{const capture={},other={},owner={pointerId:7,capture};for(const type of ['pointermove','pointerup','pointercancel']){assert.equal(ownsPointerCapture(owner,{pointerId:8,type}),false);assert.equal(ownsPointerCapture(owner,{pointerId:7,type}),true);}assert.equal(ownsPointerCapture(owner,{pointerId:7,type:'lostpointercapture',target:other}),false);assert.equal(ownsPointerCapture(owner,{pointerId:7,type:'lostpointercapture',target:capture}),true);assert.equal(ownsPointerCapture(null,{pointerId:7}),false);const recaptured={hasPointerCapture:()=>true};assert.equal(ownsPointerCapture({pointerId:7,capture:recaptured},{pointerId:7,type:'lostpointercapture',target:recaptured}),false);});
-// 成功捕获只释放一次；节点脱离导致的 set/hasPointerCapture 异常作为捕获失败或安全清理处理，不升级为业务错误。
+// held 是平台捕获状态替身：第一次释放令它变 false，第二次释放必须跳过 releasePointerCapture。
+// set/hasPointerCapture 抛出的 detached 由助手容错；这里不验证 editor 手势取消或文档修改。
 test('failed capture and detached release stay transport failures, while a held capture releases once',()=>{let held=false,releases=0;const target={setPointerCapture(){held=true;},hasPointerCapture(){return held;},releasePointerCapture(){held=false;releases++;}};assert.equal(acquirePointerCapture(target,1),true);releasePointerCapture(target,1);releasePointerCapture(target,1);assert.equal(releases,1);assert.equal(acquirePointerCapture({...target,setPointerCapture(){throw Error('detached');}},2),false);assert.doesNotThrow(()=>releasePointerCapture({...target,hasPointerCapture(){throw Error('detached');}},2));});