Fix theme pull, push, and package to cover all theme files

[karreiro]

WHY are these changes introduced?

The checksums API returns config/styles.css and AGENTS.md, but Shopify CLI does not handle them.

WHAT is this pull request doing?

Recognize config/styles.css and AGENTS.md during theme synchronization, and include both files in theme packages.

How to manually test your changes?

Run the following commands against a theme containing both files:

shopify theme pull
shopify theme push
shopify theme package

Notice that config/styles.css and AGENTS.md are pulled, pushed, and included in the generated package.

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

[Copilot]

🟢 Approval recommended

No unresolved review comments remain, and the changes include test coverage.

Pull request overview

Updates theme synchronization and packaging to support config/styles.css and root AGENTS.md.

Changes:

• Discovers, synchronizes, and orders both files.
• Includes AGENTS.md in theme packages.
• Adds fixtures, tests, and a patch changeset.

File summaries

File	Summary
packages/theme/src/cli/utilities/theme-uploader.ts	Handles upload and deletion ordering.
packages/theme/src/cli/utilities/theme-uploader.test.ts	Tests synchronization behavior.
packages/theme/src/cli/utilities/theme-fs.ts	Discovers and classifies the new files.
packages/theme/src/cli/utilities/theme-fs.test.ts	Tests filesystem discovery and classification.
packages/theme/src/cli/utilities/fixtures/theme/config/styles.css	Adds stylesheet fixture.
packages/theme/src/cli/utilities/fixtures/theme/AGENTS.md	Adds instructions fixture.
packages/theme/src/cli/services/package.ts	Includes AGENTS.md in packages.
packages/theme/src/cli/services/package.test.ts	Tests package inclusion.
.changeset/olive-themes-sync.md	Documents the user-facing patch.

Review details

• Files reviewed: 9/9 changed files
• Comments generated: 0
• Review effort level: Lite

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[karreiro]

(the changelog was applied in the patch counter part #8529)