feat: miller column browser, offline cache, search, breadcrumbs

- Dynamic miller column sizing with flexbox layout
- Root column (160px), middle slices (48px), active column (flex)
- Auto-scroll browser to rightmost column on navigation
- Offline indicator UI and IndexedDB cache integration
- /api/documents endpoint for client-side document caching
- Breadcrumb navigation in document content area
- FTS5 search with SQLite virtual table
- Client-side Mermaid and KaTeX rendering via CDN
- Deep sample content (advanced-topics/raft-deep-dive)
- Border removal (only search button keeps radius)
- Full viewport layout with proper borders between sidebar/content

apps/server/internal/httpserver/static/render.js

@@ -0,0 +1,81 @@
+(function () {
+  function renderMermaid() {
+    if (typeof mermaid === "undefined") return;
+    const blocks = document.querySelectorAll("pre code.language-mermaid");
+    blocks.forEach(function (block) {
+      const pre = block.parentElement;
+      const container = document.createElement("div");
+      container.className = "mermaid";
+      container.textContent = block.textContent;
+      pre.replaceWith(container);
+    });
+    mermaid.initialize({ startOnLoad: false });
+    mermaid.run({ querySelector: ".mermaid" });
+  }
+
+  function renderMath() {
+    if (typeof katex === "undefined") return;
+
+    const blocks = document.querySelectorAll("pre code.language-math");
+    blocks.forEach(function (block) {
+      const pre = block.parentElement;
+      const container = document.createElement("div");
+      container.className = "katex-block";
+      try {
+        katex.render(block.textContent.trim(), container, {
+          displayMode: true,
+          throwOnError: false,
+        });
+        pre.replaceWith(container);
+      } catch (e) {
+        console.warn("KaTeX render failed:", e);
+      }
+    });
+
+    const markdownBody = document.querySelector(".markdown-body");
+    if (!markdownBody) return;
+
+    const html = markdownBody.innerHTML;
+    let newHtml = html;
+
+    newHtml = newHtml.replace(/\$\$([\s\S]+?)\$\$/g, function (match, tex) {
+      try {
+        return katex.renderToString(tex.trim(), {
+          displayMode: true,
+          throwOnError: false,
+        });
+      } catch (e) {
+        return match;
+      }
+    });
+
+    newHtml = newHtml.replace(/\$([^\s$][^$]*?)\$/g, function (match, tex) {
+      try {
+        return katex.renderToString(tex.trim(), {
+          displayMode: false,
+          throwOnError: false,
+        });
+      } catch (e) {
+        return match;
+      }
+    });
+
+    if (newHtml !== html) {
+      markdownBody.innerHTML = newHtml;
+    }
+  }
+
+  function init() {
+    renderMermaid();
+    renderMath();
+  }
+
+  window.renderMermaid = renderMermaid;
+  window.renderMath = renderMath;
+
+  if (document.readyState === "loading") {
+    document.addEventListener("DOMContentLoaded", init);
+  } else {
+    init();
+  }
+})();