fix: make the reading viewport a script-driven scroll container so sticky and view timelines work

src/journey/navigation-controller.ts

@@ -99,8 +99,19 @@ const browserRuntime = (): NavigationRuntime => ({
   pushHash: (hash) => window.history.pushState(window.history.state, "", hash),
   replaceHash: (hash) =>
     window.history.replaceState(window.history.state, "", hash),
-  scrollTarget: (target, behavior) =>
-    target.scrollIntoView({ behavior, block: "start" }),
+  scrollTarget: (target, behavior) => {
+    // Inside the live reading stage the document is the only real scroller;
+    // scrollIntoView would move the script-driven inner viewport instead.
+    if (target.closest('[data-reading-stage="live"]') === null) {
+      target.scrollIntoView({ behavior, block: "start" });
+      return;
+    }
+    const margin = parseFloat(getComputedStyle(target).scrollMarginTop) || 0;
+    window.scrollTo({
+      top: window.scrollY + target.getBoundingClientRect().top - margin,
+      behavior,
+    });
+  },
   focusHeading: (target) => {
     target
       .querySelector<HTMLElement>('h1[tabindex="-1"], h2[tabindex="-1"]')