fix(web): pluralize singular subagent counts

The localized catalog exposed one count.total and one count.running string for every cardinality. The English dictionary therefore rendered both the visible trigger and its accessibility label as 1 subagents, and the assembled Web golden had begun preserving that grammar error.

Split both count families into explicit one and other keys, following the existing client locale convention. SubagentCatalogAction selects the pair from the effective descendant count; English uses subagent for one and subagents otherwise, while Chinese keeps its unchanged classifier text under the same key domain.

Add a component regression proving a single running descendant selects both singular keys. Update the real Web E2E locator and keyless assembled aria golden from 1 subagents to 1 subagent. Both ui-subagent test files pass all 28 tests and the package TypeScript project builds cleanly.

apps/web/tests/snapshots/subagent-conversation/ui.expected.md

@@ -3,8 +3,8 @@
     - button "Ask a research subagent to"
     - text: /
     - button "event-sourcing researcher" [disabled]
-  - button "1 subagents":
-    - text: 1 subagents
+  - button "1 subagent":
+    - text: 1 subagent
     - img
   - tablist:
     - tab "Chat" [selected]

apps/web/tests/subagent-conversation.e2e.ts

@@ -331,7 +331,7 @@ describe('web e2e: persisted subagent conversation and human continuation', () =
 
   it('opens an unavailable persisted grandchild after recording the available child', async () => {
     onTestFailed(() => saveFailureShot(page, 'web-e2e-subagent-grandchild'))
-    await page.getByRole('button', { name: '1 subagents' }).click()
+    await page.getByRole('button', { name: '1 subagent' }).click()
     await page.getByRole('treeitem', { name: new RegExp(NESTED_LABEL) }).click()
     await page.getByText('The parent session is offline; reopen it to continue sending messages.').waitFor()
     const hierarchy = page.getByRole('navigation', { name: 'Session hierarchy' })