Tighten store list BP test types

[alfonso-noriega]

WHY are these changes introduced?

The Business Platform store-list tests used broad as any casts for mocked GraphQL responses and captured request options. That made the tests less useful as coverage for the generated query shape.

WHAT is this pull request doing?

• Adds typed test helpers based on ListAccessibleShopsQuery.
• Replaces inline untyped response objects with those helpers.
• Replaces request-option as any casts with a small captured-request helper.

How to test your changes?

• pnpm --filter @shopify/store vitest src/cli/services/store/list/bp-source.test.ts ✅
• pnpm --filter @shopify/store type-check ✅
• pnpm --filter @shopify/store lint ✅
• git diff --check ✅

Post-release steps

None.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add