ci: run test job on ubuntu + windows matrix, fix Playwright setup for Windows

[Copilot]

Completes the CI follow-up from the Windows probe PR: adds Windows to the test matrix, makes the Playwright install OS-aware, and restores the Copilot setup workflow to Ubuntu.

Changes

• check.yml – test job matrix: Only the test job now runs on both ubuntu-latest and windows-latest (fail-fast: false). All other jobs remain Ubuntu-only.
• Codecov uploads gated to Ubuntu: Both coverage and test-result uploads have if: matrix.os == 'ubuntu-latest' to avoid duplicate uploads and OIDC failures on Windows.
• setup-playwright/action.yml – OS-aware install: --with-deps (Linux system package installs) is skipped on Windows; both OSes still use --only-shell.

  if [ "$RUNNER_OS" = "Linux" ]; then
    pnpm exec playwright install --with-deps --only-shell
  else
    pnpm exec playwright install --only-shell
  fi

• copilot-setup-steps.yml: Reverted runs-on from windows-latest back to ubuntu-latest.

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[changeset-bot]

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Latest commit: bff4d63

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[pkg-pr-new]

npm i https://pkg.pr.new/storybookjs/mcp/@storybook/addon-mcp@184

npm i https://pkg.pr.new/storybookjs/mcp/@storybook/mcp@184

commit: 0db4cfe

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
436	1	435	0

View the full list of 1 ❄️ flaky test(s)

apps/internal-storybook/tests/check-deps.e2e.test.ts > Storybook Dependencies > should be using latest versions from registry

Flake rate in main: 27.42% (Passed 45 times, Failed 17 times)

Stack Traces | 5.63s run time

Error: Storybook dependencies are outdated. Update the catalog in pnpm-workspace.yaml:

  sed -i '' 's/10\.3\.0-alpha\.12/10.3.0-alpha.13/g' pnpm-workspace.yaml && pnpm install

Outdated packages:
  - @storybook/addon-docs: 10.3.0-alpha.12 → 10.3.0-alpha.13
  - @storybook/react-vite: 10.3.0-alpha.12 → 10.3.0-alpha.13
  - storybook: 10.3.0-alpha.12 → 10.3.0-alpha.13
 ❯ tests/check-deps.e2e.test.ts:42:10

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