feat(mobile): pull-to-refresh sidebar list

- usePullToRefresh: hand-rolled hook. Records startY only when the
  scroll container is at scrollTop=0 to avoid hijacking mid-scroll
  pulls. Tracks downward delta on touchmove; fires onRefresh on
  touchend if delta >= 80px threshold. Holds the refreshing state for
  600ms minimum so the action feels intentional.
- ProjectSidebar: wires usePullToRefresh(() => retry()) on the nav
  element, mobile-only. A status indicator above the nav grows with
  pullDist (max 80px) and cycles 'Pull to refresh' -> 'Release to
  refresh' -> 'Refreshing...'. retry() is from useSidebar and refetches
  GET /api/sidebar.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/hooks/usePullToRefresh.ts

@@ -0,0 +1,77 @@
+import { useCallback, useRef, useState } from 'react';
+import type { TouchEvent } from 'react';
+
+interface Options {
+  threshold?: number;
+  enabled?: boolean;
+  maxPull?: number;
+}
+
+interface Handlers {
+  onTouchStart: (e: TouchEvent<HTMLElement>) => void;
+  onTouchMove: (e: TouchEvent<HTMLElement>) => void;
+  onTouchEnd: () => void;
+  pullDist: number;
+  refreshing: boolean;
+}
+
+// Hand-rolled pull-to-refresh: records the initial Y on touchstart only if
+// the target is scrolled to the top, then tracks downward pull on touchmove.
+// On touchend, fires onRefresh if the pull exceeded the threshold.
+export function usePullToRefresh(
+  onRefresh: () => void | Promise<void>,
+  { threshold = 80, enabled = true, maxPull = 120 }: Options = {},
+): Handlers {
+  const [pullDist, setPullDist] = useState(0);
+  const [refreshing, setRefreshing] = useState(false);
+  const startYRef = useRef<number | null>(null);
+
+  const onTouchStart = useCallback(
+    (e: TouchEvent<HTMLElement>) => {
+      if (!enabled || refreshing) return;
+      const target = e.currentTarget as HTMLElement;
+      if (target.scrollTop > 0) return;
+      const t = e.touches[0];
+      if (!t) return;
+      startYRef.current = t.clientY;
+    },
+    [enabled, refreshing],
+  );
+
+  const onTouchMove = useCallback(
+    (e: TouchEvent<HTMLElement>) => {
+      if (!enabled || refreshing || startYRef.current === null) return;
+      const t = e.touches[0];
+      if (!t) return;
+      const delta = t.clientY - startYRef.current;
+      if (delta > 0) {
+        setPullDist(Math.min(delta, maxPull));
+      } else {
+        setPullDist(0);
+      }
+    },
+    [enabled, refreshing, maxPull],
+  );
+
+  const onTouchEnd = useCallback(() => {
+    if (!enabled || refreshing) {
+      startYRef.current = null;
+      setPullDist(0);
+      return;
+    }
+    const fired = pullDist >= threshold && startYRef.current !== null;
+    startYRef.current = null;
+    setPullDist(0);
+    if (fired) {
+      setRefreshing(true);
+      Promise.resolve(onRefresh())
+        .catch(() => {})
+        .finally(() => {
+          // Hold the indicator briefly so the action feels intentional.
+          window.setTimeout(() => setRefreshing(false), 600);
+        });
+    }
+  }, [enabled, refreshing, pullDist, threshold, onRefresh]);
+
+  return { onTouchStart, onTouchMove, onTouchEnd, pullDist, refreshing };
+}