Add typed JSON output to theme share

[gonzaloriestra]

WHY are these changes introduced?

Closes https://github.com/shop/issues-develop/issues/23693

theme share creates a theme but does not declare a JSON flag or expose its result schema.

WHAT is this pull request doing?

Add --json and a discoverable share schema using the push transfer contract. Preserve random theme naming, listing selection, upload warnings/errors, and the existing terminal output.

Normal output:

The theme 'Creative Theme' (#1) was pushed successfully.

Matching JSON:

{
  "theme": {
    "id": 1,
    "name": "Creative Theme",
    "role": "unpublished",
    "shop": "example.myshopify.com",
    "editor_url": "https://example.myshopify.com/admin/themes/1/editor",
    "preview_url": "https://example.myshopify.com?preview_theme_id=1"
  }
}

Uses the draft multi-environment contract from this stack: one array in requested order, environment names on successful results, failures on stderr, [] when none succeed, and unchanged exit behavior. The shared tests also cover cancellation and analytics cleanup failures across all three commands.

How to manually test your changes?

pnpm shopify theme share --help
pnpm shopify theme share --json-schema
pnpm shopify theme share --store example.myshopify.com --path ./theme --json
pnpm shopify theme share --environment staging --environment production --force --json

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, #8643.

[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

packages/cli-kit/dist/private/node/ui/tasks.d.ts

import { TokenizedString } from '../../../public/node/output.js';
export interface Task<TContext = unknown> {
    title: string | TokenizedString;
    task: (ctx: TContext, task: Task<TContext>) => Promise<void | Task<TContext>[]>;
    retry?: number;
    retryCount?: number;
    errors?: Error[];
    skip?: (ctx: TContext) => boolean;
}
export declare function runTasks<TContext>(tasks: Task<TContext>[], onTask?: (task: Task<TContext>) => void): Promise<TContext>;

Existing type declarations

packages/cli-kit/dist/private/node/ui/components/Tasks.d.ts

@@ -1,14 +1,7 @@
 import { AbortSignal } from '../../../../public/node/abort.js';
-import { TokenizedString } from '../../../../public/node/output.js';
+import { Task } from '../tasks.js';
 import React from 'react';
-export interface Task<TContext = unknown> {
-    title: string | TokenizedString;
-    task: (ctx: TContext, task: Task<TContext>) => Promise<void | Task<TContext>[]>;
-    retry?: number;
-    retryCount?: number;
-    errors?: Error[];
-    skip?: (ctx: TContext) => boolean;
-}
+export type { Task } from '../tasks.js';
 interface TasksProps<TContext> {
     tasks: Task<TContext>[];
     silent?: boolean;