test(runtime): main 新增的 #5079 ARTIFACT-backed 用例改走 OS_METADATA_WRITABLE 逃生门

合并 origin/main 后的 jointly-wrong 破坏(AGENTS.md §10):两侧各自正确、
合起来红。main 在 meta-overlay-read-your-writes.test.ts 新增了整个
`#5079 — list / get / dispatch agree immediately after deleteMeta` describe 块,
其中 `an ARTIFACT-backed delete resets to the shipped value` 用例对一个
PACKAGED action 做 overlay 写;本 PR 把 `action` 的 allowOrgOverride 回滚为
false(#6483 裁决),该写点遂抛 NOT_OVERRIDABLE。文本合并干净,故 git 无冲突。

对齐方式沿用本 PR 已提交的同类处置(#4521 块中的同形用例):打开
`OS_METADATA_WRITABLE` 运营逃生门并重置两处 memoised 缓存,配 afterEach 清理,
避免 action 可写性泄漏到相邻用例。该 describe 块其余用例写的都是全新名字,
走 allowRuntimeCreate,不受回滚影响,故只此一处需要逃生门。

pnpm --filter @objectstack/runtime test: 115 files / 1733 tests 全绿。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011sGk4SKHqGRgmmqUok1P8M

Author: claude

packages/runtime/src/meta-overlay-read-your-writes.test.ts

@@ -346,11 +346,31 @@ describe('#5079 — list / get / dispatch agree immediately after deleteMeta', (
         expect((await surfaces('only_one')).listedNames).toEqual([]);
     });
 
+    afterEach(() => {
+        // The escape-hatch case below must not leak `action` writability into
+        // its neighbours — both memoised caches, or the next case lies.
+        delete process.env.OS_METADATA_WRITABLE;
+        (ObjectStackProtocolImplementation as any).resetEnvWritableCache();
+        resetEnvWritableMetadataTypes();
+    });
+
     it('an ARTIFACT-backed delete resets to the shipped value — it does not retire the name', async () => {
         // The boundary the #5079 fix must not cross. `removeRuntimeShadow`
         // still owns this case; `removeOverlayEntry` must never reach it, or a
         // "reset to artifact default" would delete the artifact instead of
         // revealing it.
+        //
+        // #6483 rolled `action`'s `allowOrgOverride` back to `false`
+        // (ADR-0005: page/app/action are ❌ in the amendment table), so
+        // overriding this PACKAGED action needs the one documented door that
+        // remains — the `OS_METADATA_WRITABLE` operator escape hatch, exactly
+        // as the sibling `#4521` case above does. (Every other case in this
+        // block writes brand-new names, which ride `allowRuntimeCreate`
+        // untouched, so only this one needs the hatch.)
+        process.env.OS_METADATA_WRITABLE = 'action';
+        (ObjectStackProtocolImplementation as any).resetEnvWritableCache();
+        resetEnvWritableMetadataTypes();
+
         registry.registerItem(
             'action',
             { name: 'shipped_probe', label: 'Shipped', type: 'script', target: 'showcase.shipped' },