Add AGENT.md (symlink to CLAUDE.md?)

overall it could be just minimalistic one as I made for https://github.com/datalad/datalad/blob/maint/CLAUDE.md where we would point to existing DEVELOPMENT.md

@bendichter as you are the main AI-powered contributor, what would you suggest in addition/instead? what is yours looks like? @dandi/dandi-archive do you use/have any?

Read the existing DEVELOPMENT.md and compare it with the linked Datalad CLAUDE.md example. Decide whether AGENT.md should be a symlink to CLAUDE.md or a minimal pointer to DEVELOPMENT.md, then confirm the chosen convention is documented and the new file provides the intended agent guidance.

Written by the indexing model from the issue text.