fix(example-showcase): translate the task dataset's done_count and done_rate labels at birth

The two dataset measures the done rate moved into are declared surface under
the i18n coverage ratchet, so they carry en and zh-CN bundle entries; the
showcase's untranslated count is back at its baseline.

Claude-Session: https://claude.ai/code/session_01Sfe5YjBLwB9J3y8fvm2xq1
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

examples/app-showcase/src/system/translations/index.ts

@@ -348,6 +348,18 @@ export const ShowcaseTranslationBundle = {
         },
       },
     },
+    // Translated at birth, same rule as the widgets above: the done rate moved
+    // here from the delivery cube (#20943) as two new dataset measures, born
+    // under the ratchet. The task dataset's older labels predate it and stay in
+    // the frozen baseline.
+    datasets: {
+      showcase_task_metrics: {
+        measures: {
+          done_count: { label: 'Done Tasks' },
+          done_rate: { label: 'Done Rate' },
+        },
+      },
+    },
   },
   'zh-CN': {
     objects: {
@@ -1018,6 +1030,16 @@ export const ShowcaseTranslationBundle = {
         },
       },
     },
+    // The done rate's two measures, translated at birth (#20943) — see the `en`
+    // block. The other task-dataset labels stay in the frozen baseline.
+    datasets: {
+      showcase_task_metrics: {
+        measures: {
+          done_count: { label: '已完成任务' },
+          done_rate: { label: '完成率' },
+        },
+      },
+    },
     // Page component copy became declared surface with `pages.<name>.components`
     // (#6080), so these keys are born under the ratchet: leaving any of them
     // untranslated widens the frozen baseline and fails `check-i18n-coverage`.