fix(frontend): a paused schedule can be deleted from the panel but not resumed there

A paused schedule now appears in the Schedules panel, and the only actions on its row are View and Delete — resuming exists only in copilot chat.

#14416 makes paused schedules visible for the first time (before, the listing dropped anything with no next run). GraphScheduleListItem labels the row "Paused" and offers the same two actions it offers a live one. So a user who paused a schedule and wants it back finds no control for that, and the nearest thing on the row is Delete — which loses the cadence permanently and cannot be undone.

The gap is narrow by construction: the paused rows that show up are ones the user paused themselves, and they paused them in chat, where resume_schedule is available. But the panel is where someone goes looking.

Two options, cheapest first: a tooltip on the "Paused" label saying it can be resumed from chat, or a Resume action on the row. The second needs a REST endpoint — pause and resume are copilot-tool-only today, wrapping the scheduler client — so it is the larger change and the better one.

Related: #14577, which is why a deliberate pause cannot be told apart from an archive pause in the first place.

Found by the autoreviewer on #14416 (, explicitly non-blocking for that PR's scope).