"Saved" is a moment, top-right, and gone in five seconds

it was a permanent line under the controls saying "Saved." — which said nothing,
because everything on this screen has been saved, all the time. it looked exactly
like feedback, so the one moment it actually meant something was indistinguishable
from every moment it did not.

now it appears when a save LANDS and clears itself. top-right of the block, beside
the title rather than in the flow: it is a remark about the block, not part of what
you are doing, and inline it pushes everything below down a line and then pulls it
back up — a layout that jumps every time somebody saves.

"Not set yet" stays. that IS a state, and it is the one worth knowing; it goes when
it stops being true rather than being replaced by a line that never changes.

the timer is a ref and is cleared before each new one. without that, saving twice
in quick succession leaves the first timeout running and it fires against the
second save — the confirmation vanishing a moment after appearing, which reads as
the second save failing.

Block moved to its own file and each setting now renders its own. the status belongs
to the setting that produced it, and lifting one block's timer into the panel would
put it in a component with nothing to do with it. that is also what made the
top-right slot possible without absolutely positioning anything.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/useFlash.ts

@@ -0,0 +1,33 @@
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+/**
+ * A message that shows itself and then goes away — "Saved", and whatever joins it.
+ *
+ * ── Why this is not a piece of state somebody sets and clears ──
+ *
+ * The timer is held in a ref and CLEARED before each new one is set. Without that, saving twice in
+ * quick succession leaves the first timeout running, and it fires against the second save — the
+ * confirmation vanishes a moment after appearing, which looks like the second save failed.
+ *
+ * The cleanup on unmount matters for the same reason it always does: this lives in a panel that is
+ * swapped out whenever the nav moves, and a timeout that outlives its component sets state on nothing.
+ */
+export const useFlash = (ms = 5000) => {
+  const [showing, setShowing] = useState(false);
+  const timer = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+  const clear = () => {
+    if (timer.current) clearTimeout(timer.current);
+    timer.current = null;
+  };
+
+  const flash = useCallback(() => {
+    clear();
+    setShowing(true);
+    timer.current = setTimeout(() => setShowing(false), ms);
+  }, [ms]);
+
+  useEffect(() => clear, []);
+
+  return [showing, flash] as const;
+};