default locale 'en-CA' → an unambiguous YYYY-MM-DD — not defaulted to 'th-TH' because ICU
would automatically interpret the calendar as the Buddhist era (e.g. 2569 instead of 2026),
which isn't always what a user wants; the Thai locale/calendar can be chosen explicitly via
DateFormat.locale (e.g. 'th-TH-u-ca-buddhist') — per concept.md, which specifies this must
live in the formatter config, not be hardcoded in the resolver
default locale 'en-CA' → an unambiguous YYYY-MM-DD — not defaulted to 'th-TH' because ICU would automatically interpret the calendar as the Buddhist era (e.g. 2569 instead of 2026), which isn't always what a user wants; the Thai locale/calendar can be chosen explicitly via DateFormat.locale (e.g. 'th-TH-u-ca-buddhist') — per concept.md, which specifies this must live in the formatter config, not be hardcoded in the resolver