fix(web): preserve sidebar width across views and refreshes

Drags on zoomed/HiDPI displays persist fractional widths (clientX is
fractional), and readSidebarWidth's Number.isInteger guard rejected them,
silently resetting the sidebar to the default width on every panel mount
(view switch or refresh). Round on write so stored widths stay canonical,
and accept any finite stored value on read (round + clamp) so
already-persisted fractional values heal instead of resetting.

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

Author: tyler-dane

packages/web/src/components/PlannerSidebar/storage/sidebar-width.storage.test.ts

@@ -35,9 +35,24 @@ describe("sidebar width storage", () => {
     expect(readSidebarWidth()).toBe(SIDEBAR_MAX_WIDTH);
   });
 
+  it("rounds fractional stored widths instead of resetting to the default", () => {
+    // Drags on zoomed/HiDPI displays used to persist values like "400.5",
+    // which the old integer-only guard rejected — resetting the sidebar on
+    // every view switch and refresh.
+    localStorage.setItem(STORAGE_KEYS.SIDEBAR_WIDTH, "400.5");
+
+    expect(readSidebarWidth()).toBe(401);
+  });
+
   it("writes widths through the storage abstraction", () => {
     writeSidebarWidth(360);
 
     expect(localStorage.getItem(STORAGE_KEYS.SIDEBAR_WIDTH)).toBe("360");
   });
+
+  it("rounds fractional widths on write", () => {
+    writeSidebarWidth(400.5);
+
+    expect(localStorage.getItem(STORAGE_KEYS.SIDEBAR_WIDTH)).toBe("401");
+  });
 });

packages/web/src/components/PlannerSidebar/storage/sidebar-width.storage.ts

@@ -9,12 +9,17 @@ export function readSidebarWidth(): number {
   const stored = persistentBrowserStore.get(STORAGE_KEYS.SIDEBAR_WIDTH);
   if (stored === null) return SIDEBAR_DEFAULT_WIDTH;
 
+  // Drags on zoomed/HiDPI displays produce fractional widths, so tolerate
+  // (and heal) any finite stored value instead of resetting to the default.
   const width = Number(stored);
-  return Number.isInteger(width)
-    ? clampSidebarWidth(width)
+  return Number.isFinite(width)
+    ? clampSidebarWidth(Math.round(width))
     : SIDEBAR_DEFAULT_WIDTH;
 }
 
 export function writeSidebarWidth(width: number): void {
-  persistentBrowserStore.set(STORAGE_KEYS.SIDEBAR_WIDTH, String(width));
+  persistentBrowserStore.set(
+    STORAGE_KEYS.SIDEBAR_WIDTH,
+    String(Math.round(width)),
+  );
 }