Validate section setting keys in JSON templates

[chippleh1392]

What are you adding in this PR?

Fixes #1239.

ValidSettingsKey already validates setting keys inside section schema presets/defaults, but template JSON section settings were not checked. That meant a template could set an unknown section setting key and Theme Check would report no offense.

This adds the JSON-template side of the same check for templates/*.json:

• resolve each template section's type to its section schema
• validate sections.*.settings keys against that schema's settings
• report the unknown key on the template JSON setting key

This covers section settings and template block settings, including nested blocks. Section group JSON files are left unchanged.

What's next? Any followup issues?

No follow-up planned.

What did you learn?

Template JSON checks run separately from Liquid schema checks, so this uses a JSON companion check registered under the same ValidSettingsKey code.

Tophatting

• corepack pnpm exec vitest run packages/theme-check-common/src/checks/valid-settings-key/index.spec.ts
• corepack pnpm exec vitest run packages/theme-check-common/src/index.spec.ts packages/theme-check-common/src/checks/valid-settings-key/index.spec.ts
• corepack pnpm --dir packages/theme-check-common type-check
• corepack pnpm exec prettier --check --ignore-unknown packages/theme-check-common/src/checks/valid-settings-key/index.ts packages/theme-check-common/src/checks/valid-settings-key/index.spec.ts packages/theme-check-common/src/checks/index.ts .changeset/bright-keys-check.md
• corepack pnpm build from Git Bash on Windows
• I added screenshots of the changes (before and after the changes if applicable)

Before you deploy

• This PR includes a new checks or changes the configuration of a check
  • I included a minor bump changeset
  • I ran pnpm build and committed the updated configuration files (no tracked config changes were produced)
  • If applicable, I've updated the theme-app-extension.yml config (not applicable)
  • [Shopifolk] I've made a PR to update the shopify.dev theme check docs if applicable.

[domaine-stijn-slats]

Hi @chippleh1392,

Thanks for the PR!

What about blocks in templates?

[chippleh1392]

Hi @domaine-stijn-slats, good point. I extended the JSON template path to cover block settings too, using the same general traversal shape as JSONMissingBlock.

This now checks section settings and template block settings under sections.*.blocks.*.settings, including nested blocks. Local blocks and theme blocks are resolved separately. I kept section group JSON out of scope for parity with JSONMissingBlock, but can include that too if you want it covered here.