Suggest shopify store open for previewing created preview store

[amcaplan]

WHY are these changes introduced?

When shopify store create preview finishes, the first suggested next step was to open a raw storefront URL. For preview stores that link can be tokenized/unresolved, and it doesn't give users (or agents) a repeatable, copyable command. Now that shopify store open exists, the next-steps output should point at that command so previewing a store is consistent with the other suggested commands (store execute, theme pull/push).

WHAT is this pull request doing?

Updates the first next step emitted by previewStoreNextSteps in packages/store/src/cli/services/store/create/preview/result.ts:

• Before: Open your store (<storefrontUrl>) to preview the storefront. (rendered a direct link to the storefront URL)
• After: Use `shopify store open --store <subdomain>` to preview the storefront. (rendered as a command token in text output, and as the backtick-quoted command in JSON output)

This makes the storefront step a copyable command keyed off the store subdomain, matching the format of the other two next steps.

Tests in result.test.ts were updated to assert the new JSON string and the {command: ...} text token, and the JSON test case was renamed from "with the storefront URL" to "with the next steps".

How to test your changes?

1. Run shopify store create preview (or run the preview-store result suite).
2. Confirm the first next step reads: Use `shopify store open --store <subdomain>` to preview the storefront.
3. Confirm both text and JSON (--json) output reflect the command rather than a storefront URL.
4. pnpm vitest packages/store/src/cli/services/store/create/preview/result.test.ts

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 — shopify store open is still a hidden command, so the suggestion is not yet public; no changeset added.

[amcaplan]

• Suggest shopify store open for previewing created preview store #7969 👈 (View in Graphite)
• Add shopify store open command #7955 : 1 other dependent PR (#7956 )
• main

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[amcaplan]

/snapit

[github-actions]

🫰✨ Thanks @amcaplan! Your snapshot has been published to npm.

Test the snapshot by installing your package globally:

pnpm i -g --@shopify:registry=https://registry.npmjs.org @shopify/cli@0.0.0-snapshot-20260630184011

Caution

After installing, validate the version by running shopify version in your terminal.
If the versions don't match, you might have multiple global instances installed.
Use which shopify to find out which one you are running and uninstall it.