Add typed JSON output to theme open

[gonzaloriestra]

WHY are these changes introduced?

theme open only prints links for humans. Scripts need a typed, discoverable result containing the selected theme and its URLs.

Part of https://github.com/shop/issues-develop/issues/23695.

WHAT is this pull request doing?

Add --json and a domain-owned result schema. Keep theme selection, terminal text, and browser opening behavior unchanged, with separate execution and presentation.

Normal output:

Preview information for theme 'My theme' (#1)
• Preview your theme
• Customize your theme at the theme editor

JSON output:

{
  "theme": {
    "id": 1,
    "name": "My theme",
    "createdAtRuntime": false,
    "processing": false,
    "role": "unpublished"
  },
  "preview_url": "https://store.myshopify.com?preview_theme_id=1",
  "editor_url": "https://store.myshopify.com/admin/themes/1/editor"
}

The optional theme.src field is included when available. Refresh the command manifest, README, and generated documentation. Add service, schema, presentation, and real stdout/stderr tests.

How to manually test your changes?

pnpm shopify theme open --store YOUR_STORE --theme YOUR_THEME
pnpm shopify theme open --store YOUR_STORE --theme YOUR_THEME --editor
pnpm shopify theme open --store YOUR_STORE --theme YOUR_THEME --json
pnpm shopify theme open --help
pnpm shopify theme open --json-schema

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
• A single changeset for all theme migrations is added in the last PR, #8682.

[github-actions]

Differences in type declarations

We detected differences in the type declarations generated by Typescript for this branch compared to the baseline ('main' branch). Please, review them to ensure they are backward-compatible. Here are some important things to keep in mind:

• Some seemingly private modules might be re-exported through public modules.
• If the branch is behind main you might see odd diffs, rebase main into this branch.

New type declarations

We found no new type declarations in this PR

Existing type declarations

packages/cli-kit/dist/public/node/base-command.d.ts

@@ -35,6 +35,7 @@ declare abstract class BaseCommand extends Command {
         argv: string[];
     }>;
     protected environmentsFilename(): string | undefined;
+    protected validateNonTTYFlags(flags: FlagOutput): void;
     protected failMissingNonTTYFlags(flags: FlagOutput, requiredFlags: string[]): void;
     private failMissingNonTTYFlagRequirements;
     private applicableNonTTYFlagRequirements;