[locale] change abbreviation of august for Indonesian locale - #6197

Thank you for contributing this correction! I’m using AI to assist with this review because I’m not a native Indonesian speaker, so I checked the proposal against external sources rather than relying on my own language knowledge.

The formatting change from Agt to Agu looks correct:

• Unicode CLDR specifies Agu as the abbreviated Indonesian name for August in both formatting and stand-alone contexts: https://raw.githubusercontent.com/unicode-org/cldr-json/main/cldr-json/cldr-dates-full/main/id/ca-gregorian.json
• Indonesia’s National Library OPAC also displays dates using Agu, for example 18-Agu-2026: https://opac.perpusnas.go.id/

I noticed one compatibility issue with parsing. Existing Moment releases accept Agt, but this change would make it invalid. For example:

moment('Agt', 'MMM', 'id', true).isValid(); // currently true

Could you keep Agt as a parsing alias while changing formatted output to Agu? I would also like the parsing tests to cover both the preferred Agu form and the legacy Agt form.

Please also remove the generated changes under dist/, locale/, and min/, then commit those updates and rebase the PR on the latest develop branch. Only src/locale/id.js and src/test/locale/id.js should remain in the PR; generated files are updated as part of the release process.

Thanks again. The core correction is well-supported, and preserving the old parsing form should make it safe for existing users.