fix: moving focus as episodes load, loading indicator

src/hooks/useHeldFlag.ts

@@ -0,0 +1,46 @@
+/**
+ * useHeldFlag — keep a boolean true for a minimum time after it falls.
+ *
+ * A warm-cache fetch-more load begins and ends between two renderer
+ * frames: the raw `isLoadingMore` signal flips true→false without a
+ * single paint, so the "[Fetch More]" → spinner swap never appears and
+ * the press looks like a no-op. Components rendering a spinner for such
+ * bursts read through this hook instead of the raw signal — the spinner
+ * stays up (and animating) for at least `minMs` after the load ends,
+ * guaranteeing several painted frames.
+ *
+ * Deliberately a display-layer concern: the store's own `isLoadingMore`
+ * keeps its exact load-window semantics (guards, tests) and only the
+ * rendered indicators are held.
+ */
+import { createSignal, createEffect, onCleanup } from "solid-js";
+
+export function useHeldFlag(
+ source: () => boolean,
+ minMs = 250,
+): () => boolean {
+ const [held, setHeld] = createSignal(false);
+ let timer: ReturnType<typeof setTimeout> | null = null;
+ const clearTimer = () => {
+  if (timer) {
+   clearTimeout(timer);
+   timer = null;
+  }
+ };
+
+ createEffect(() => {
+  if (source()) {
+   // (Re)rising edge: show immediately; a pending fall from an
+   // earlier burst is cancelled.
+   clearTimer();
+   if (!held()) setHeld(true);
+  } else if (held()) {
+   // Falling edge: hold the flag up for the remaining window.
+   clearTimer();
+   timer = setTimeout(() => setHeld(false), minMs);
+  }
+ });
+
+ onCleanup(clearTimer);
+ return held;
+}