Preview Stores prototype: add preview create / execute / claim

[dmerand]

WHY are these changes introduced?

This is the companion CLI half of the original Preview Stores prototype.

The paired World PR (shop/world#708792) adds local preview-store orchestration endpoints. This branch adds the CLI commands needed to exercise that flow end-to-end from a local CLI checkout:

• shopify preview create
• shopify preview execute
• shopify preview claim

This is a prototype branch, not a ship candidate.

WHAT is this pull request doing?

• adds the preview command surface in the CLI
• wraps the local Core preview-store endpoints
• supports:
  • creating a preview store
  • running Admin GraphQL against the preview store with an explicit token
  • claiming/transferring the preview store through the existing handoff flow
• keeps the auth model intentionally simple for the first prototype: explicit token + magic-link handoff

This is the parent PR for the auth-bootstrap follow-up in #7574.

How to test your changes?

With the paired World branch from shop/world#708792 running locally:

cd /Users/donald/src/github.com/Shopify/cli
pnpm install
pnpm --filter @shopify/cli build

node packages/cli/bin/dev.js preview create --shop-name preview-demo --json
node packages/cli/bin/dev.js preview execute --from-file /tmp/preview.json --query 'query { shop { name } }' --json
node packages/cli/bin/dev.js preview claim --shop-id <shop_id> --recipient-email merchant@example.com --json

Post-release steps

None. This is prototype-only work and is not intended to ship as-is.

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 — no changeset added because this is a prototype stack paired to local-only World endpoints and is not intended to ship as-is

[dmerand]

• Preview Stores prototype: import CLI and store auth bootstrap #7574
• Preview Stores prototype: add preview create / execute / claim #7573 👈 (View in Graphite)
• main

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