feat: pro: pane-aware responsiveness, scoped sidebar overlay, stable pane keys

hooks/use-media-query.ts

@@ -2,6 +2,7 @@
 
 import { useCallback, useEffect, useSyncExternalStore } from "react";
 import { useUIStore } from "@/stores/ui-store";
+import { usePaneSize } from "@/hooks/use-pane-size";
 
 // Tailwind v4 breakpoints
 const BREAKPOINTS = {
@@ -38,12 +39,38 @@ export function useMediaQuery(query: string): boolean {
   return useSyncExternalStore(subscribe, getSnapshot, getMediaQueryServerSnapshot);
 }
 
+/**
+ * When the Pro shell renders a page inside a (possibly split) pane, that pane
+ * publishes its measured width via `PaneSizeContext`. Inner pages should
+ * branch their layout against the pane width — not the full viewport — so a
+ * narrow pane gets the mobile/tablet layout instead of overflowing.
+ *
+ * Returns `null` when no pane size is published, signalling the caller to
+ * fall back to `window.matchMedia`.
+ */
+function classifyPane(paneWidth: number | null) {
+  if (paneWidth === null) return null;
+  return {
+    isMobile: paneWidth < BREAKPOINTS.md,
+    isTablet: paneWidth >= BREAKPOINTS.md && paneWidth < BREAKPOINTS.lg,
+    isDesktop: paneWidth >= BREAKPOINTS.lg,
+  };
+}
+
 /**
  * Hook to detect device type and sync with UI store
  * Uses Tailwind breakpoints: mobile < 768px, tablet 768-1024px, desktop > 1024px
+ *
+ * When invoked inside a Pro pane, the returned values reflect the pane's
+ * width instead of the window's. The global UI store is NOT updated in that
+ * case — two split panes would otherwise fight to write conflicting values,
+ * and the store is meant to mirror the actual viewport for callers that read
+ * it directly (mobile navigation helpers etc.).
  */
 export function useDeviceDetection() {
   const { setDeviceType, isMobile, isTablet, isDesktop } = useUIStore();
+  const paneWidth = usePaneSize();
+  const paneClassification = classifyPane(paneWidth);
 
   const isMobileQuery = useMediaQuery(`(max-width: ${BREAKPOINTS.md - 1}px)`);
   const isTabletQuery = useMediaQuery(
@@ -52,9 +79,11 @@ export function useDeviceDetection() {
   const isDesktopQuery = useMediaQuery(`(min-width: ${BREAKPOINTS.lg}px)`);
 
   useEffect(() => {
+    if (paneClassification) return;
     setDeviceType(isMobileQuery, isTabletQuery, isDesktopQuery);
-  }, [isMobileQuery, isTabletQuery, isDesktopQuery, setDeviceType]);
+  }, [isMobileQuery, isTabletQuery, isDesktopQuery, setDeviceType, paneClassification]);
 
+  if (paneClassification) return paneClassification;
   return { isMobile, isTablet, isDesktop };
 }
 
@@ -62,19 +91,29 @@ export function useDeviceDetection() {
  * Convenience hooks for specific breakpoints
  */
 export function useIsMobile() {
-  return useMediaQuery(`(max-width: ${BREAKPOINTS.md - 1}px)`);
+  const paneWidth = usePaneSize();
+  const viewport = useMediaQuery(`(max-width: ${BREAKPOINTS.md - 1}px)`);
+  return paneWidth !== null ? paneWidth < BREAKPOINTS.md : viewport;
 }
 
 export function useIsTablet() {
-  return useMediaQuery(
+  const paneWidth = usePaneSize();
+  const viewport = useMediaQuery(
     `(min-width: ${BREAKPOINTS.md}px) and (max-width: ${BREAKPOINTS.lg - 1}px)`
   );
+  return paneWidth !== null
+    ? paneWidth >= BREAKPOINTS.md && paneWidth < BREAKPOINTS.lg
+    : viewport;
 }
 
 export function useIsDesktop() {
-  return useMediaQuery(`(min-width: ${BREAKPOINTS.lg}px)`);
+  const paneWidth = usePaneSize();
+  const viewport = useMediaQuery(`(min-width: ${BREAKPOINTS.lg}px)`);
+  return paneWidth !== null ? paneWidth >= BREAKPOINTS.lg : viewport;
 }
 
 export function useBreakpoint(breakpoint: keyof typeof BREAKPOINTS) {
-  return useMediaQuery(`(min-width: ${BREAKPOINTS[breakpoint]}px)`);
+  const paneWidth = usePaneSize();
+  const viewport = useMediaQuery(`(min-width: ${BREAKPOINTS[breakpoint]}px)`);
+  return paneWidth !== null ? paneWidth >= BREAKPOINTS[breakpoint] : viewport;
 }

hooks/use-pane-size.ts

@@ -0,0 +1,14 @@
+"use client";
+
+import { createContext, useContext } from "react";
+
+/**
+ * Width of the pane that's hosting the current subtree, in CSS pixels.
+ * `null` means "no pane is providing a size" — fall back to viewport-based
+ * media queries. Set by the Pro shell on each split pane via ResizeObserver.
+ */
+export const PaneSizeContext = createContext<number | null>(null);
+
+export function usePaneSize(): number | null {
+  return useContext(PaneSizeContext);
+}