OpenCode: bind a resumed session at plugin startup

A resumed OpenCode session emits no session.created and no session.status
until the first prompt, so the plugin never bound and messages waited for
the user to type. The launcher now passes HCOM_RESUME_SESSION_ID (always
set for OpenCode/Kilo, empty unless resuming, so nested launches don't
inherit it) and the plugin binds and delivers pending messages at load.