feat(lists): read and show the list cap on every capped list

Twelve routes answer a capped list with meta.truncated / meta.limit on
the envelope, and the web client read only data, so no surface said a
list had stopped short. apiGetList / apiPostList are now the one client
reader of the cap and ListCapNotice the one line that shows it; every
capped list on the web reads its cap and shows the notice under the list,
the paged readers (side effects, illness episodes) stop on the route's
answer instead of a full-page guess, and the ECG list moves its five
readers onto one hook. The record activity feed sent its cap twice, in
data and on the envelope; it rides the envelope alone now. A guard
derives the capped routes from the tree and binds each to a client that
reads its cap.

src/app/api/account/activity/route.ts

@@ -142,13 +142,9 @@ export const GET = apiHandler(async () => {
     createdAt: row.createdAt.toISOString(),
   }));
 
-  // Exact: one row past the cap was asked for, so a list that is exactly
-  // full no longer reads as cut.
-  const truncated = cap.truncated;
-
   annotate({
     action: { name: "sharing.activity.list" },
-    meta: { entry_count: entries.length, truncated },
+    meta: { entry_count: entries.length, truncated: cap.truncated },
   });
 
   return apiListSuccess(
@@ -157,11 +153,9 @@ export const GET = apiHandler(async () => {
       // The bound the view states out loud. Resolved here so the UI never has to
       // hardcode a number the operator can change.
       retentionDays,
-      // Whether the list is everything inside that window, or its most recent
-      // hundred rows. The view says which; silence would let the oldest line
-      // read as the beginning.
-      truncated,
     },
+    // Whether the list is everything inside that window, or its most recent
+    // hundred rows, rides the envelope like every capped list's (`meta`).
     cap,
   );
 });