handle_list_schedules took no requester and returned every schedule
unfiltered, unlike cancel_schedule/edit_schedule/fire_schedule_now
which all gate on the shared ownership predicate (self, operator, or
subtree via topology::is_descendant_of). list_schedules now filters
through the same predicate, renamed cancel_authorized ->
schedule_authorized since it backs all four verbs now, not just
cancel.
Fixed five stale 'every schedule' / 'unfiltered' claims found while in
here: filter_ghost_schedule_targets's doc comment, the list_schedules
MCP tool description, docs/tools/scheduling.md's per-verb section
(already self-contradicting its own top-of-file subtree-scoping claim
before this fix), and hive-core-agent-sock's ListSchedules/Schedules
wire-type doc comments (including a stale '(privileged)' marker from
the pre-topology-subtree model).
Credit to atlas: independently found the same fix while finishing
PR #4233 (which documents this bug per mara's 'fix it, don't document
it' ruling) and caught two stale doc spots I'd missed
(hive-core-agent-sock's comments) plus proposed the
schedule_authorized rename. Compared diffs directly before either of
us pushed; he dropped his scheduling.rs changes so we didn't collide.
fixes#4237