refactor: implement scroll container context and flex layout

Switch from fixed positioning to a flexbox-based layout for the
main application structure. This introduces a `ScrollContainerCtx` to
provide access to the main scrollable element, allowing child
components like `FileTree` and `RevealManager` to perform accurate
scrolling and positioning relative to the container instead of the
window.

refactor: set JournalPanel height to full

src/components/FileTree.tsx

@@ -1,6 +1,7 @@
 import { Component, createMemo, createSignal, Show } from "solid-js";
 import { type FileNode, type TocNode } from "../data-loader";
 import { useNavigateWithParams } from "./useNavigateWithParams";
+import { useScrollContainer } from "../App";
 
 /**
  * 检查当前文件路径是否在文件夹内
@@ -98,6 +99,8 @@ export const HeadingNode: Component<{
       setIsExpanded(!isExpanded());
     }
   };
+  const scrollContainer = useScrollContainer();
+
   const handleClick = (e: MouseEvent) => {
     e.preventDefault();
     navigate(href);
@@ -105,10 +108,18 @@ export const HeadingNode: Component<{
     requestAnimationFrame(() => {
       const element = document.getElementById(anchor);
       if (element) {
+        const scroller = scrollContainer();
         const navBarHeight = 80;
         const elementPosition = element.getBoundingClientRect().top;
-        const offsetPosition = window.scrollY + elementPosition - navBarHeight;
-        window.scrollTo({ top: offsetPosition, behavior: "instant" });
+        const containerTop = scroller?.getBoundingClientRect().top ?? 0;
+        const relativePosition = elementPosition - containerTop;
+        const currentScroll = scroller?.scrollTop ?? window.scrollY;
+        const offsetPosition = currentScroll + relativePosition - navBarHeight;
+        if (scroller) {
+          scroller.scrollTo({ top: offsetPosition, behavior: "instant" });
+        } else {
+          window.scrollTo({ top: offsetPosition, behavior: "instant" });
+        }
       }
     });
   };