Tighten preview store client test types

[alfonso-noriega]

WHY are these changes introduced?

No issue.

The preview-store client tests used an as any cast in the in-memory storage helper even though the helper only stores a cliInstanceId string.

WHAT is this pull request doing?

Add a narrow test storage schema and type the in-memory storage helper around the cliInstanceId key.

The helper now avoids the as any cast and more closely matches the LocalStorage methods used by the production code.

How to test your changes?

• pnpm nx run store:lint --skip-nx-cache
• pnpm --dir packages/store vitest run src/cli/services/store/create/preview/client.test.ts

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

Not user-facing; no changeset needed.

[alfonso-noriega]

• Tighten preview store client test types #7890 👈 (View in Graphite)
• main

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