[Refactor] Reuse webview test query client helper

[zoomote]

Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Added exported createTestQueryClient() to webview-ui/src/utils/test-utils.tsx and reused it inside the shared Testing Library render wrapper.
• Removed redundant manual QueryClientProvider setup from ContextWindowProgress.spec.tsx and ChatRow.subtask-links.spec.tsx so those specs rely on the shared render wrapper.

Why this change was made

This continues the approved test-utils rollout with an independent webview slice while the first pilot PR stays mergeable. The goal is still narrow: remove mechanical provider duplication without hiding test intent.

Impact

No user-facing behavior change. Webview tests get a clearer shared provider pattern, and the touched specs passed along with webview lint, typecheck, and the full Zoo-Code test suite.

Related PRs

• Zoo-Code async-stream test-utils pilot: [Refactor] Pilot shared stream test utilities #1086

[zoomote]

No code issues found. See task

_{Reviewed 1bd964b}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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