v1.10.0

v1.10.0 — one instruction setting, and it keeps itself current

agent.instruction now carries where the document comes from (text, file,
oci://, https://, or a served resource — short form classified, long form
explicit), how current to keep it (refresh: auto picks inotify for a file,
nothing for a digest pin, polling only for a mutable reference), and what to
do when the source stops answering (keep | freeze | drain | exit).

An instruction that names no source is refused, and startup on an unreachable
source stays fatal: an agent without its instructions is not an agent.