new `hyperhive.claudeMarketplaces` option (list of strings — URL,
path, or github:owner/repo). harness boot adds each via
`claude plugin marketplace add` before updating + installing the
configured plugins, so specs like `foo@some-marketplace` resolve
on a fresh container. idempotent: 'already exists' stderr is
treated as success.
install_configured now takes an optional notify recipient. on a
non-zero or spawn-failed 'claude plugin install', sub-agents send
the spec + stderr to manager via the hyperhive socket; manager
passes None so it doesn't message itself. boot still proceeds either
way — notification is best-effort.
new hyperhive.claudePlugins NixOS option (list of strings) rendered
to /etc/hyperhive/claude-plugins.json. both hive-ag3nt and hive-m1nd
shell out 'claude plugin install <spec>' for each entry once at
startup before the turn loop opens. failures log a warning but don't
abort boot.
