As usual, I overthought this completely.

curl https://micro.blog/micropub -d “h=entry” -d @yourblogpost.md -H “Authorization: Bearer BIGNUMBERHERE”

…does the trick, which is push yourblogpost.md to micro.blog. That will teach me to check the local docs first before ranging all over the Internet. I could conceivably use vim to write a post and then dump the buffer into a simple shellscript containing the curl bits above.

The folks here have made generating auth bearer tokens (BIGNUMBERHERE) a snap, so no need to dig through the Indieweb docs, hack up someone else’s xmlrpc code, or otherwise break a sweat.