Fix theme-check-disable-next-line inside tags

[andershagbard]

Summary

• theme-check-disable-next-line silently had no effect when the tag it targeted was nested inside a raw HTML tag (<style>, <script>, <svg>) — e.g. disabling PaginationSize on a {% paginate %} tag used to generate CSS custom properties inside a <style> block.
• Root cause: getNextNode() in disabled-checks/index.ts looks for the disable comment's next sibling via a children array on the parent node. Liquid nodes nested inside raw HTML tags aren't stored under children — they live under RawMarkup.nodes (see HtmlRawNode.body: RawMarkup / RawMarkup.nodes in liquid-html-parser/src/ast.ts). Since 'children' in parentNode was false for a RawMarkup parent, getNextNode returned undefined, so findNextLinePosition never registered a disabled range at all, and the offense was reported as if no disable comment existed.
• Fix: add a fallback branch that reads parentNode.nodes when present, mirroring the existing children/markup handling.

Reported by a user hitting this with:

<style>
  ...
  {%- # theme-check-disable-next-line PaginationSize -%}
  {%- paginate metaobjects.swatch.values by 9999 -%}
    ...
  {%- endpaginate -%}
</style>

Confirmed via shopify theme check --output json against a real theme file, then reduced to a minimal repro and traced to the AST-shape mismatch above.

Test plan

• Added a regression test covering disable-next-line nested in both <style> and <script>.
• disabled-checks/index.spec.ts — all 19 tests pass.
• Full theme-check-common suite — 1251 tests pass.
• tsc --noEmit clean.
• Added a changeset (patch bump for @shopify/theme-check-common).