Improve JSON schema error messages

[Barefoot0]

WHY are these changes introduced?

Fixes #22951

TOML app module validation could report confusing JSON Schema errors such as Expected object, received object when a TOML array of tables was used where an object was expected.

WHAT is this pull request doing?

• Updates JSON Schema validation error formatting to report arrays as arrayinstead of relying on JavaScript typeof output.
• Adds a TOML-specific hint for app configuration errors when an object was expected but an array was received.
• Adds regression tests for array/null received-type formatting and the TOML validation hint.

How to test your changes?

• pnpm --filter @shopify/cli-kit vitest src/public/node/json-schema.test.ts
• pnpm --filter @shopify/app vitest src/cli/services/validate.test.ts
• Can run Shopify CLI locally with a local app module and verify validation. I followed this document to set up a local test app and used this command in your cli repo: SHOPIFY_CLI_NEVER_USE_PARTNERS_API=1 SHOPIFY_SERVICE_ENV=local pnpm shopify app dev --path [path to test app]

Post-release steps

None.

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

[Barefoot0]

• Improve JSON schema error messages #7782 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.