[Security] Fix command injection risk in cloudflared installer

[gonzaloriestra]

WHY are these changes introduced?

Fixes a potential command injection vulnerability in the Cloudflare installer. The previous implementation used execSync with a template literal containing a variable derived from an environment variable (SHOPIFY_CLI_CLOUDFLARED_PATH), which could be exploited to execute arbitrary commands if the environment was compromised.

WHAT is this pull request doing?

• Replaces direct child_process.execSync and child_process.execFileSync calls with secure wrappers exec and captureOutputWithExitCode from @shopify/cli-kit/node/system.
• Switched to argument-list-based command execution for tar to prevent shell injection.
• Removed direct child_process imports to ensure all command executions go through @shopify/cli-kit which implements checkCommandSafety.
• Updated unit tests in install-cloudflared.test.ts to match the new asynchronous implementation and use the correct mocks.

How to test your changes?

Run the unit tests for the affected package:

pnpm --filter @shopify/plugin-cloudflare vitest run

Duplicate check

• Closest prior PRs:
  • [Security] Add command safety check to execCommand #7448: "[Security] Add command safety check to execCommand" - This PR added a generic safety check to the internal wrapper but did not address direct child_process usage in plugins which bypasses those checks.
  • [Security] Fix command injection in treeKill utility #7430: "[Security] Fix command injection in treeKill utility" - This PR addressed a similar vulnerability in a different utility.

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

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PR created automatically by Jules for task 17491907231653004163 started by @gonzaloriestra

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