fix(reader): restore scrollable focus-mode layout

Author: Jacobinwwey

src/frontend/styles.css

@@ -879,6 +879,7 @@ div.tooltip {
   display: flex;
   flex-direction: column;
   overflow: hidden;
+  min-height: 0;
   transition: all 0.3s ease;
 }
 
@@ -944,6 +945,76 @@ div.tooltip {
   font-family: "Segoe UI", sans-serif;
   line-height: 1.6;
   flex: 1;
+  min-height: 0;
+}
+
+.reading-layout {
+  display: flex;
+  flex: 1;
+  min-height: 0;
+  overflow: hidden;
+}
+
+.reading-main {
+  display: flex;
+  flex: 1 1 auto;
+  flex-direction: column;
+  min-width: 0;
+  min-height: 0;
+}
+
+.reading-diagnostics {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  padding: 8px 18px 0;
+  flex-shrink: 0;
+}
+
+.reading-diagnostics-item {
+  display: inline-flex;
+  align-items: center;
+  min-height: 24px;
+  padding: 2px 8px;
+  border-radius: 999px;
+  background: rgba(60, 60, 60, 0.9);
+  color: #cfd8e3;
+  font-size: 0.78rem;
+}
+
+.reading-outline {
+  width: 240px;
+  min-width: 200px;
+  max-width: 280px;
+  border-left: 1px solid #333;
+  background: rgba(20, 20, 20, 0.82);
+  display: flex;
+  flex-direction: column;
+  flex-shrink: 0;
+  min-height: 0;
+}
+
+.reading-outline-header {
+  padding: 14px 16px 10px;
+  color: #8ddcff;
+  font-size: 0.82rem;
+  font-weight: 700;
+  letter-spacing: 0.04em;
+  text-transform: uppercase;
+  border-bottom: 1px solid #2e2e2e;
+}
+
+.reading-outline-body {
+  flex: 1;
+  min-height: 0;
+  overflow-y: auto;
+  padding: 10px 12px 14px;
+}
+
+.reading-outline-empty {
+  color: #8c99a7;
+  font-size: 0.82rem;
+  line-height: 1.5;
 }
 
 /* Content Styling */
@@ -1165,6 +1236,19 @@ div.tooltip {
     height: 90%;
   }
 
+  .reading-layout {
+    flex-direction: column;
+  }
+
+  .reading-outline {
+    width: 100%;
+    max-width: none;
+    min-width: 0;
+    max-height: 180px;
+    border-left: none;
+    border-top: 1px solid #333;
+  }
+
   /* 4. Top Bar Adjustments */
   #source-control {
     left: 70px; /* Make room for menu button */