swarm-ui: a schedules page, one card per scheduled prompt

/schedules lists the controller's scheduled prompts as cards: name as the
title, the agents it fires for, the message, its cadence and next fire.
Edit turns a card into its own form; pause, resume and remove act in place,
and + schedule opens an empty form. The form sends only what changed, so a
rename never moves the fire times, and warns when the start or the repeat
does. Filters reuse the shared card filter bar.

Adds a TextAreaField to the ui kit, and an upcoming mode on RelativeTime so
a next-fire time reads "in 5m". Needs the controller's /api/schedules
routes.

frontend/packages/swarm-ui/src/ui/relative-time/RelativeTime.tsx

@@ -9,14 +9,24 @@
 // package's matrix-rain effect — and resyncs immediately on becoming
 // visible again instead of waiting out the rest of a stale interval.
 import { useEffect, useState } from "preact/hooks";
-import { fmtAgo } from "../../util.js";
+import { fmtAgo, fmtUntil } from "../../util.js";
 
 // Cheap at the handful of rows/chips this renders for today, and coarse
 // enough to be correct without visibly ticking every frame — the same
 // choice a wall clock makes.
 const TICK_MS = 1000;
 
-export function RelativeTime({ epochMs }: { epochMs: number }) {
+// `upcoming`: the instant is expected to be ahead (a schedule's next fire),
+// so one still ahead reads "in 5m" instead of clamping to "0s ago". Off by
+// default, so a caller showing an age never sees a skewed clock turn it
+// into a countdown.
+export function RelativeTime({
+  epochMs,
+  upcoming = false,
+}: {
+  epochMs: number;
+  upcoming?: boolean;
+}) {
   const [now, setNow] = useState(() => Date.now());
 
   useEffect(() => {
@@ -43,5 +53,8 @@ export function RelativeTime({ epochMs }: { epochMs: number }) {
     };
   }, []);
 
-  return <>{fmtAgo((now - epochMs) / 1000)}</>;
+  const ageSeconds = (now - epochMs) / 1000;
+  return (
+    <>{upcoming && ageSeconds < 0 ? fmtUntil(-ageSeconds) : fmtAgo(ageSeconds)}</>
+  );
 }