theme-check incorrectly flags options_by_name keys containing spaces as invalid

Describe the bug
When a quoted string including a space is included within the opening line of a forloop, theme-check incorrectly reports is as invalid syntax.

Source

{%- for value in product.options_by_name['hello world'].values -%}
  {{ value }}
{%- endfor -%}

Expected behaviour

The syntax is fine - there are no issues using this syntax in a theme, so there should be no reported theme-check errors.

Actual behaviour

A syntax error is reported after the space in the quoted string.

Also when theme-check tries to autofix the error on save, it actually creates broken syntax.

The snippet described earlier gets "corrected" to

{%- for value in product.options_by_name['hello -%}
  {{ value }}
{%- endfor -%}

I suspect simply not flagging the error to begin would prevent this.

Debugging information

• OS [e.g. Windows, Mac, Linux]: Mac
• OS Version: Tahoe 26.3.1 (a)
• Theme Check Version [e.g. 0.1.0]: 3.94.1 (shopify-cli, I'm not sure if theme check has a different version or where I'd find it)

Reproduce the reported Liquid for-loop in theme-check 3.94.1 and trace the parser or diagnostic path handling bracketed keys with spaces. Add a regression test for the valid options_by_name['hello world'] expression, then verify that linting reports no error and autofix does not alter the syntax.