Say how often, and say what a reschedule costs

Occurrence ids carry their own start day, so moving the anchor or the
interval re-keys every occurrence and the marks under the old ids stop
being reachable. Nothing is rewritten — removeEvent makes the same trade,
and useMarkSet never removes because nothing else holds a copy — but the
reader is told the count first, the way removeGame reports blockedBy
instead of cascading.

Informs, never blocks. Renaming still costs nothing: the token is random
precisely so fixing a typo never moves an id, and movesOccurrences is what
keeps the warning off a rename and off a bare change of `until`.

cadenceLabel sits beside the form's own vocabulary so the sheet cannot
describe a rule differently from the control that set it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/client/components/EventDetail.tsx

@@ -7,7 +7,7 @@ import {
   type LaneId,
 } from "../../shared/custom.ts";
 import type { EventDraft } from "../state/useCustom.ts";
-import { EventForm } from "./CustomForms.tsx";
+import { cadenceLabel, EventForm } from "./CustomForms.tsx";
 import {
   formatAbsolute,
   formatRemaining,
@@ -76,6 +76,7 @@ export function EventDetail({
         games: CustomGames;
         onSave: (id: string, draft: EventDraft) => void;
         onDelete: (id: string) => void;
+        strandedBy: (draft: EventDraft) => number;
       }
     | undefined;
 }) {
@@ -159,6 +160,10 @@ export function EventDetail({
           <Field label="Type">{event.type}</Field>
         </dl>
 
+        {cadenceLabel(own?.record.repeat ?? null) !== null && (
+          <p className="text-xs text-faint">{cadenceLabel(own!.record.repeat)}</p>
+        )}
+
         {risk !== "fine" && effort !== undefined && clock.msRemaining !== null && (
           <p
             className="mt-4 rounded-lg border px-3 py-2 text-xs leading-relaxed"
@@ -241,6 +246,7 @@ export function EventDetail({
                   setEditing(false);
                 }}
                 onCancel={() => setEditing(false)}
+                strandedBy={own.strandedBy}
               />
             ) : (
               <div className="flex gap-2">