test(lib-guards): lib 产物缺失时 chunk-artifact / manifest-consistency 跳过而非 ENOENT

fresh clone 未 build 直接 pnpm test 时，两 spec 的 readFileSync 会
ENOENT 崩溃（此前靠 package.json prepare 钩子隐式兜底）。改为文件级
describe.skipIf 守卫：缺产物时整套显示为 skipped 并 console 提示先
pnpm build（exit 0）；产物存在时行为与之前完全一致（本仓 prepare 钩
子产出 lib 后两 spec 照常执行，已验证 9 passed 非 skipped）。

tests/chunk-artifact.spec.ts

@@ -5,8 +5,10 @@
  * be callable with a require that resolves the platform externals — the
  * exact shape the loader (src/client/chunk-loader.ts) depends on. Reads the
  * built lib/ output, so run `pnpm build` first (like manifest-consistency).
+ * A missing lib/ (fresh clone before the first build) skips the whole suite
+ * instead of crashing on ENOENT.
  */
-import { readFileSync } from 'node:fs'
+import { existsSync, readFileSync } from 'node:fs'
 import { describe, expect, it } from 'vitest'
 // Browser globals first: chunk bodies probe `self`/`document` at evaluation
 // (xterm's UMD wrapper, CodeMirror's UA probe).
@@ -17,7 +19,14 @@ const g = globalThis as Record<string, unknown>
 
 const CHUNKS = ['terminal', 'editor', 'mermaid']
 
-describe('built chunk artifacts', () => {
+/** All chunk artifacts present (tsdown emits the whole lib/ in one run). */
+const chunksBuilt = CHUNKS.every(name => existsSync(`lib/client-${name}.js`))
+
+if (!chunksBuilt) {
+  console.warn('[chunk-artifact] lib/ chunk artifacts missing — run `pnpm build` first; skipping this suite')
+}
+
+describe.skipIf(!chunksBuilt)('built chunk artifacts', () => {
   it('each chunk assigns its global registry slot when executed as a script', () => {
     g.window = g // classic-script globals
     // mermaid's core hooks window.addEventListener('load') at module scope

tests/manifest-consistency.spec.ts

@@ -11,7 +11,9 @@
  *   bundles must never be swapped.
  *
  * Reads the built lib/ output, so run `pnpm build` first (the registry
- * install validates main/client.main existence the same way).
+ * install validates main/client.main existence the same way). A missing
+ * lib/ (fresh clone before the first build) skips the whole suite instead
+ * of crashing on ENOENT.
  */
 import { describe, expect, it } from 'vitest'
 import { existsSync, readFileSync } from 'node:fs'
@@ -20,6 +22,13 @@ import { fileURLToPath } from 'node:url'
 
 const ROOT = resolve(fileURLToPath(new URL('..', import.meta.url)))
 
+/** The build output is present (tsdown emits the whole lib/ in one run). */
+const libBuilt = existsSync(resolve(ROOT, 'lib/client.js'))
+
+if (!libBuilt) {
+  console.warn('[manifest-consistency] lib/ build output missing — run `pnpm build` first; skipping this suite')
+}
+
 /** The registry manifest face this spec touches (mirror of the registry's PluginManifest). */
 interface PluginManifest {
   id: string
@@ -72,7 +81,7 @@ function chunkSlot(file: string): string {
   return match[1]!
 }
 
-describe('registry manifest consistency (dsh.plugin.json)', () => {
+describe.skipIf(!libBuilt)('registry manifest consistency (dsh.plugin.json)', () => {
   it('id is a valid two-segment registry id (native form)', () => {
     expect(manifest.id).toMatch(ID_PATTERN)
   })