docs(tests): explain size history traversal and recovery capture semantics

tests/headless/recovery-encoding.test.mjs

@@ -61,7 +61,7 @@ test('cooperative sealing captures unknown values before yielding and retains ex
  assert.deepEqual(calls,['getter','left','right']);
  mutable.title='outside';current='outside';
  const image=await pending;
- // A second uncached table below exercises the work ceiling with a coarse clock.
+ // 下方另造未预热的大表，用静止时钟隔离工作量上限；即使时间预算不增长也必须让出。
  assert.ok(yields>0);assert.deepEqual(image,expected);assert.equal(isSealedRecoveryImage(image),true);
  assert.equal(sealedRecoveryByteLength(image),new TextEncoder().encode(JSON.stringify(image)).byteLength);
  const beforeCoarse=yields;
@@ -82,6 +82,7 @@ test('cooperative preparation evaluates every unsafe occurrence and rejects erro
  await assert.rejects(sealRecoveryImageAsync(17,1,1,dataArray(Array.from({length:1000},(_,i)=>i)),{now:()=>ticks++,frameBudgetMs:1,yieldTask:async()=>{throw Error('yield_failed');}}),/yield_failed/);
  // 异步深度检查使用内部 dataRecord 包装；省略的对象字段和变成 null 的数组项占用深度不同。
  const nested=(n,leaf)=>{for(let i=0;i<n;i++)leaf=dataRecord({child:leaf});return leaf;};
+ // 预热 leaf 只允许复用编码内容，不能把它的高度从外层深度预算中抹去。
  const leaf=freeze({value:1});encodeRecoveryValue(leaf);
  await assert.rejects(sealRecoveryImageAsync(17,1,1,nested(64,leaf)),/invalid_recovery_payload/);
  await assert.rejects(sealRecoveryImageAsync(17,1,1,nested(64,dataArray([undefined]))),/invalid_recovery_payload/);
@@ -126,7 +127,7 @@ test('repeated owned containers reuse facts assembled earlier in the same asynch
  assert.ok(yields>0);assert.equal(image.payload.left,image.payload.right);
  assert.equal(image.payload.left.length,1000);assert.equal(image.payload.left[999].index,999);
  assert.equal(sealedRecoveryByteLength(image),new TextEncoder().encode(JSON.stringify(image)).byteLength);
- // Unsafe descendants still need independent values for every occurrence.
+ // 相同容器身份不代表后代 getter 安全；每次出现仍需独立捕获，递增值必须依次为 1、2。
  let n=0;const unsafe=dataRecord({getValue:Object.freeze({get value(){return ++n;}})});
  const captured=await sealRecoveryImageAsync(17,1,1,dataArray([unsafe,unsafe]));
  assert.deepEqual(captured.payload,[{getValue:{value:1}},{getValue:{value:2}}]);
@@ -171,6 +172,7 @@ test('unknown callbacks invalidate the detached JSON environment without changin
  // left 先捕获，bridge getter 改写数组 toJSON，right 后捕获；同一 image 内顺序变化必须与同步 codec 一致。
  const make=async()=>dataRecord({left:await ownedRecord(),bridge:{get value(){Object.defineProperty(Array.prototype,'toJSON',{configurable:true,value(){return ['changed-by-callback'];}});return 'bridge';}},right:await ownedRecord()});
  try{
+  // 同步参照也会改写原型，先 cleanup 再构造异步输入，保证两次捕获从相同环境开始。
   const expected=sealRecoveryImage(17,1,1,await make());cleanup();
   const payload=await make();let tick=0,yields=0;
   const pending=sealRecoveryImageAsync(17,1,1,payload,{now:()=>tick++,frameBudgetMs:1,yieldTask:async()=>{yields++;}});