fix: 真正的流式输出 + 修复 Markdown 标题渲染

流式输出:
- 恢复 content 事件处理，实时累积 LLM 原始输出
- parsePartialJSON 从不完整 JSON 中渐进提取已闭合的字段
- 每次提取到新字段即更新两栏，实现左栏渐进渲染
- 结构化事件(title/detail等)覆盖解析结果，确保最终一致

Markdown 渲染:
- 重写为逐行处理(_renderLines)，不再按双换行分块
- ### 及更深层级标题在单换行后也能正确识别为独立块
- 列表项、水平线等同样受益于逐行解析

static/js/markdown.js

@@ -29,10 +29,8 @@ const Markdown = {
             .replace(/</g, '&lt;')
             .replace(/>/g, '&gt;');
 
-        // Phase 4: Block-level processing (split into blocks by blank lines)
-        const blocks = text.split(/\n{2,}/);
-        const htmlBlocks = blocks.map(block => this._renderBlock(block.trim()));
-        text = htmlBlocks.join('\n');
+        // Phase 4: Block-level processing (line-by-line to handle single-newline headers/lists)
+        text = this._renderLines(text);
 
         // Phase 5: Restore fenced code blocks
         codeBlocks.forEach((cb, idx) => {
@@ -55,39 +53,63 @@ const Markdown = {
         return text;
     },
 
+    _renderLines(text) {
+        const lines = text.split('\n');
+        const out = [];
+        let para = [];
+
+        const flushPara = () => {
+            if (para.length) {
+                out.push(`<p class="md-p">${this._renderInline(para.join('<br>'))}</p>`);
+                para = [];
+            }
+        };
+
+        for (const line of lines) {
+            const trimmed = line.trim();
+
+            // Blank line — flush paragraph
+            if (!trimmed) { flushPara(); continue; }
+
+            // Horizontal rule
+            if (/^(-{3,}|\*{3,}|_{3,})$/.test(trimmed)) { flushPara(); out.push('<hr class="md-hr">'); continue; }
+
+            // Header (h1–h6)
+            const hm = trimmed.match(/^(#{1,6}) (.+)$/);
+            if (hm) { flushPara(); out.push(`<h${hm[1].length} class="md-h${hm[1].length}">${this._renderInline(hm[2])}</h${hm[1].length}>`); continue; }
+
+            // Blockquote
+            if (/^&gt;\s?/.test(trimmed)) { flushPara(); out.push(`<blockquote class="md-blockquote">${this._renderInline(trimmed.replace(/^&gt;\s?/, ''))}</blockquote>`); continue; }
+
+            // Unordered list item
+            if (/^[\-\*]\s/.test(trimmed)) { flushPara(); out.push(this._renderListItem(trimmed, 'ul')); continue; }
+
+            // Ordered list item
+            if (/^\d+\.\s/.test(trimmed)) { flushPara(); out.push(this._renderListItem(trimmed, 'ol')); continue; }
+
+            // Regular text — accumulate into paragraph
+            para.push(trimmed);
+        }
+        flushPara();
+        return out.join('\n');
+    },
+
+    _renderListItem(line, tag) {
+        const m = line.match(/^[\s]*(?:[\-\*]|\d+\.)\s+(.*)$/);
+        const content = m ? m[1] : line;
+        // Return just the li; caller can wrap in ul/ol if needed
+        return `<li class="md-li">${this._renderInline(content)}</li>`;
+    },
+
     _renderBlock(block) {
+        // Kept as fallback; primary rendering now uses _renderLines
         if (!block) return '';
-
-        // Horizontal rule
-        if (/^(-{3,}|\*{3,}|_{3,})$/.test(block)) {
-            return '<hr class="md-hr">';
-        }
-
-        // Headers
-        const headerMatch = block.match(/^(#{1,6}) (.+)$/);
-        if (headerMatch) {
-            const level = headerMatch[1].length;
-            const content = this._renderInline(headerMatch[2]);
-            return `<h${level} class="md-h${level}">${content}</h${level}>`;
-        }
-
-        // Blockquote
-        if (/^&gt;\s?/.test(block)) {
-            const inner = block.replace(/^&gt;\s?/gm, '').trim();
-            return `<blockquote class="md-blockquote">${this._renderInline(inner)}</blockquote>`;
-        }
-
-        // Unordered list
-        if (/^[\-\*]\s/.test(block)) {
-            return this._renderList(block, 'ul');
-        }
-
-        // Ordered list
-        if (/^\d+\.\s/.test(block)) {
-            return this._renderList(block, 'ol');
-        }
-
-        // Paragraph
+        if (/^(-{3,}|\*{3,}|_{3,})$/.test(block)) return '<hr class="md-hr">';
+        const hm = block.match(/^(#{1,6}) (.+)$/);
+        if (hm) return `<h${hm[1].length} class="md-h${hm[1].length}">${this._renderInline(hm[2])}</h${hm[1].length}>`;
+        if (/^&gt;\s?/.test(block)) { const inner = block.replace(/^&gt;\s?/gm, '').trim(); return `<blockquote class="md-blockquote">${this._renderInline(inner)}</blockquote>`; }
+        if (/^[\-\*]\s/.test(block)) return this._renderList(block, 'ul');
+        if (/^\d+\.\s/.test(block)) return this._renderList(block, 'ol');
         return `<p class="md-p">${this._renderInline(block)}</p>`;
     },