feat: story-journey immersive layer (progress, scene focus, floating orbs)

themes/dreamscape/assets/css/dreamscape.css

@@ -253,6 +253,121 @@ main {
     font-family: var(--font-sans);
 }
 
+/* ═══ 故事沉浸层（文章页） ═══ */
+.story-journey {
+    position: relative;
+    isolation: isolate;
+}
+
+.story-orb {
+    position: fixed;
+    pointer-events: none;
+    z-index: -1;
+    border-radius: 50%;
+    filter: blur(36px);
+    opacity: 0.35;
+    mix-blend-mode: screen;
+    transition: transform 0.2s ease-out;
+}
+
+.orb-1 {
+    width: 280px;
+    height: 280px;
+    top: 14%;
+    left: -80px;
+    background: radial-gradient(circle, rgba(123,104,238,0.42), transparent 70%);
+}
+
+.orb-2 {
+    width: 220px;
+    height: 220px;
+    top: 48%;
+    right: -60px;
+    background: radial-gradient(circle, rgba(34,211,238,0.34), transparent 72%);
+}
+
+.orb-3 {
+    width: 320px;
+    height: 320px;
+    bottom: 6%;
+    left: 24%;
+    background: radial-gradient(circle, rgba(74,144,217,0.30), transparent 72%);
+}
+
+.story-progress {
+    position: sticky;
+    top: 62px;
+    height: 4px;
+    background: rgba(123,104,238,0.18);
+    border-radius: 999px;
+    overflow: hidden;
+    margin: -1rem 0 2rem;
+    z-index: 40;
+}
+
+.story-progress-bar {
+    height: 100%;
+    width: 0%;
+    background: linear-gradient(90deg, var(--glow-purple), var(--glow-cyan));
+    box-shadow: 0 0 18px rgba(123,104,238,0.6);
+    transition: width 0.08s linear;
+}
+
+/* 场景段落：像旅程节点 */
+.article-body > p {
+    position: relative;
+    padding-left: 1.1rem;
+}
+
+.article-body > p::before {
+    content: '';
+    position: absolute;
+    left: -0.15rem;
+    top: 0.85rem;
+    width: 6px;
+    height: 6px;
+    border-radius: 50%;
+    background: var(--glow-purple);
+    box-shadow: 0 0 12px rgba(123,104,238,0.8);
+    opacity: 0.55;
+}
+
+.article-body > p.active-scene::before {
+    background: var(--glow-cyan);
+    box-shadow: 0 0 16px rgba(34,211,238,0.9);
+    opacity: 1;
+}
+
+.article-body > p.active-scene {
+    text-shadow: 0 0 18px rgba(123,104,238,0.22);
+}
+
+/* 手机端沉浸优化 */
+@media (max-width: 640px) {
+    .story-progress {
+        top: 54px;
+        margin: -0.5rem 0 1.2rem;
+    }
+    .story-orb {
+        filter: blur(26px);
+        opacity: 0.28;
+    }
+    .orb-1 { width: 180px; height: 180px; left: -60px; }
+    .orb-2 { width: 150px; height: 150px; right: -45px; }
+    .orb-3 { width: 190px; height: 190px; left: 20%; }
+}
+
+/* 降级策略：用户偏好减少动画 */
+@media (prefers-reduced-motion: reduce) {
+    .story-orb,
+    .story-progress-bar,
+    .reveal,
+    .js-ready .article-body p {
+        animation: none !important;
+        transition: none !important;
+    }
+}
+
 /* ═══ 文章页 ═══ */
 .dream-article {
     padding-top: 2rem;