fix(qa/dogfood): showcase 端点 fixture 显式声明它不携带 functions,而不是靠 JSON.stringify 偷偷丢掉

`showcase-declarative-endpoints.dogfood.test.ts` 用
`JSON.stringify(showcaseStack)` 手搓一份 artifact 顶替 `objectstack build`,
但只做了后者的一半:真实构建先跑 `lowerCallables` 把每个 callable 换成字符串
ref,并把函数本体放进 sibling ESM 模块;`JSON.stringify` 没有这一步,它只是把
函数值的键整个省略。

于是这份 artifact 从来就没携带过 showcase 的任何 function —— 它只是"看起来"
携带了:裸条目(`sweepProjectHealth: fn`)连键一起消失,剩下 `functions: {}`,
照样 parse 通过。两个函数都被静默丢弃,没人看得见。

showcase 换成诚实的声明形之后这份静默就破了:`{ handler: fn, effect: 'writes' }`
会保留对象、只丢 `handler`,留下 `{ effect: 'writes' }` —— 一个为自己并不携带
的函数声明了 effect 的条目,`FlowFunctionEntrySchema` 四个成员一致拒收,完全
正确。

改为显式剔除 `functions` 并写明原因:本 boot 真正运行的函数来自交给
`bootStack` 的**活栈**,不来自这个文件;该文件的职责是把 `apis:` 块喂给
`MetadataPlugin`。静默丢失变成声明式省略。

Author: claude

packages/qa/dogfood/test/showcase-declarative-endpoints.dogfood.test.ts

@@ -103,7 +103,27 @@ beforeAll(async () => {
   process.chdir(SHOWCASE_DIR);
   tempDir = mkdtempSync(join(tmpdir(), 'os-e8-endpoints-'));
   const artifactPath = join(tempDir, 'objectstack.json');
-  writeFileSync(artifactPath, JSON.stringify(showcaseStack));
+  // `functions` is dropped DELIBERATELY, and saying so is the point (#4976).
+  //
+  // This line stands in for `objectstack build`, but it is only half of it: the
+  // real build runs `lowerCallables` first, replacing every callable with a
+  // string ref and carrying the functions themselves in a sibling ESM module.
+  // A plain `JSON.stringify` has no such step — it simply omits function-valued
+  // keys — so this artifact never carried the showcase's functions at all. It
+  // merely LOOKED like it did, because a bare entry (`sweepProjectHealth: fn`)
+  // vanishes key and all and leaves `functions: {}` behind, which parses.
+  //
+  // That silence broke the moment the showcase spelled its writer the honest,
+  // declared way: `{ handler: fn, effect: 'writes' }` keeps the object and drops
+  // only `handler`, leaving `{ effect: 'writes' }` — an entry declaring an
+  // effect for a function it does not carry, which `FlowFunctionEntrySchema`
+  // refuses in all four of its members, exactly as it should.
+  //
+  // Nothing is lost by omitting the key: the functions this boot actually runs
+  // come from the LIVE stack handed to `bootStack` below, not from this file,
+  // whose job is to give `MetadataPlugin` the `apis:` block to ingest.
+  const { functions: _functionsLiveOnly, ...artifact } = showcaseStack as Record<string, unknown>;
+  writeFileSync(artifactPath, JSON.stringify(artifact));
 
   stack = await bootStack(showcaseStack, {
     // The `flow`-typed endpoint delegates to `IAutomationService.execute`;