Missing agent.name field

Hi,

The endpoint datastreams are missing the `agent.name` field in the documents. Normally any document ingested by Elastic Agent using an Integration has `agent.name` available.

For some datastreams `agent.name` already exists in the mapping:
https://github.com/elastic/endpoint-package/blob/master/package/endpoint/data_stream/process/fields/fields.yml#L50

Review package/endpoint/data_stream/process/fields/fields.yml and start with the existing agent.name mapping referenced in the issue. Compare the datastream mappings to identify which ones lack the field; done means the affected ingested documents expose agent.name consistently.

Written by the indexing model from the issue text.