Extends the salvaged #64229 ledger (PR #76490) to cover the registries
added on main since the PR was cut, and lands the remaining Phase 0
lifecycle pieces:
- register_system_prompt_section and register_approval_transport now
record ownership handles, so unload/force-reload removes plugin
system prompt sections and approval transports too
- ctx.on_unload(callback): plugin cleanup callbacks run through the
reverse-order ledger walk, exception-isolated
- ctx.spawn_task(coro): supervised background asyncio tasks tracked in
the ledger and cancelled on unload
- document the #65593 multi-profile constraint on the ledger (keyed per
manager/(hermes_home, plugin_id); identity-conditional restores) with
a TODO(#64178) for full profile keying of remaining global slots
Part of #64229; prerequisite for #64178.
Teknium