fix(skin): 修复最终评审发现的 6 处缺陷（junction 排除失效/meta 静默丢失等）

跨任务视角发现的问题：Critical1 materialize.mjs 的 junction 排除比较在
Windows 上因长路径前缀恒假、从未生效，且测试夹具的 junction 指向真源自身，
掩盖了此问题；Critical2 composeSkin 例外通道在 uuid 缺失/框架侧无 meta 时
静默失败，违反第二准则；Important3 可覆盖范围误把 theme/ 下的框架 TS 代码
也纳入；Important5 cli-entry 测试漏注册 check-skin/build-game；Important6
composeSkin 与 check-skin 各自拼路径，未共用 paths.mjs 权威推导；Important7
--platform 缺值时静默落到默认平台。逐条修复并补测试，Critical1 用诱饵框架
目录验证过能真正杀掉该 bug（变异推演见 fix report）。

spec §5 step5 的 dist/<name>/ 拷贝按要求标注为本期未实现，不实现。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

cocoscreator_projects/scripts/test/skin.test.mjs

@@ -4,7 +4,7 @@ import { join } from 'node:path';
 import { mkdirSync, writeFileSync, rmSync, mkdtempSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { deflateSync } from 'node:zlib';
-import { listAssets, readPngSize, validateOverrides } from '../lib/skin.mjs';
+import { listAssets, listCoverableAssets, readPngSize, validateOverrides } from '../lib/skin.mjs';
 
 // ---- 测试辅助：零依赖生成指定尺寸的 PNG ----
 function crc32(buf) {
@@ -59,6 +59,36 @@ test('listAssets 对不存在的目录返回空数组', () => {
   assert.deepEqual(listAssets('/no/such/dir'), []);
 });
 
+// ---- listCoverableAssets：Important 3——可覆盖范围须限定为 spec §2 规则 3 的 8 个目录 ----
+test('listCoverableAssets 排除 theme/ 与 README.md，只保留 8 个白名单目录下的资源', () => {
+  const d = makeDirs();
+  try {
+    png(d.fw, 'atlas-hall/btn.png');
+    writeFile(d.fw, 'README.md', '# framework ui');
+    writeFile(d.fw, 'theme/default-theme.ts', 'export const DEFAULT_THEME = {};');
+    writeFile(d.fw, 'theme/types.ts', 'export interface ThemeConfig {}');
+    const covered = listCoverableAssets(d.fw).sort();
+    assert.deepEqual(covered, ['atlas-hall/btn.png']);
+    assert.ok(!covered.some((f) => f.startsWith('theme/')), 'theme/ 下的框架代码不属于可覆盖资源');
+    assert.ok(!covered.includes('README.md'), 'README.md 不是可覆盖资源');
+  } finally { cleanup(d.root); }
+});
+
+test('validateOverrides：override 放一个 .ts 到 theme/ 会被判为 orphan（不在可覆盖范围内）', () => {
+  const d = makeDirs();
+  try {
+    png(d.fw, 'atlas-hall/btn.png');
+    writeFile(d.fw, 'theme/resolve-theme.ts', 'export function resolveTheme() {}');
+    // 子游戏企图覆盖框架代码
+    writeFile(d.ov, 'theme/resolve-theme.ts', 'export function resolveTheme() { /* hijacked */ }');
+    const r = validateOverrides(d.fw, d.ov);
+    assert.equal(r.errors.length, 1);
+    assert.equal(r.errors[0].code, 'orphan');
+    assert.equal(r.errors[0].path, 'theme/resolve-theme.ts');
+    assert.equal(r.matched.length, 0, 'theme 覆盖不应被当作合法命中');
+  } finally { cleanup(d.root); }
+});
+
 // ---- readPngSize ----
 test('readPngSize 读出宽高；非 PNG 返回 null', () => {
   const d = makeDirs();