[jm-rivera]

internal_error now maps on datasets.pin at 500, in registries/codes.json and its packaged copy.

dfo-apis answers CallerUnresolved as a non-retryable internal_error 500 on every door. Each of its causes is a deployment fault a retry does not clear: a principal mismatch, an unset DFO_CALLER_HMAC_KEY, or a missing or bad trusted X-Forwarded-For entry. The Datasets doors answered it as service_unavailable 503 with retryable: false, which contradicts that code's definition ("a retry is expected to succeed"). internal_error already maps at 500 on datasets.exports, datasets.export_link, presentation.write and presentation.shares; datasets.pin was the one door without it.

Testing: validate_registry passes (265 entries), and the spec-kit (450) and dfo-spec-kit-components (314) tests pass.