Add Markdown import from Obsidian (Stage 8)

- md-to-tiptap.ts: remark-based converter (headings, lists, blockquotes,
  code blocks, bold/italic/strike, links, images, hr)
- Obsidian ![[wikilink]] stripped, [[link|alias]] → plain text
- POST /api/admin/import-md: parses frontmatter (gray-matter) + converts content
- LessonEditor: "Импорт .md" button populates editor without auto-save
- ROADMAP: marked Stages 2, 3, 5, 6, 7, 8 as complete, fixed numbering

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/md-to-tiptap.ts

@@ -0,0 +1,188 @@
+import { unified } from "unified";
+import remarkParse from "remark-parse";
+
+// ── Types ─────────────────────────────────────────────────────────────────────
+
+type Mark = { type: string; attrs?: Record<string, unknown> };
+
+type TipTapNode = {
+  type: string;
+  attrs?: Record<string, unknown>;
+  content?: TipTapNode[];
+  text?: string;
+  marks?: Mark[];
+};
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type MdastNode = Record<string, any>;
+
+// ── Inline converter ──────────────────────────────────────────────────────────
+
+function convertInline(nodes: MdastNode[], marks: Mark[] = []): TipTapNode[] {
+  const result: TipTapNode[] = [];
+
+  for (const node of nodes) {
+    switch (node.type) {
+      case "text": {
+        if (!node.value) break;
+        const n: TipTapNode = { type: "text", text: node.value as string };
+        if (marks.length) n.marks = marks;
+        result.push(n);
+        break;
+      }
+
+      case "strong":
+        result.push(...convertInline(node.children, [...marks, { type: "bold" }]));
+        break;
+
+      case "emphasis":
+        result.push(...convertInline(node.children, [...marks, { type: "italic" }]));
+        break;
+
+      case "delete":
+        result.push(...convertInline(node.children, [...marks, { type: "strike" }]));
+        break;
+
+      case "inlineCode":
+        result.push({
+          type: "text",
+          text: node.value as string,
+          marks: [...marks, { type: "code" }],
+        });
+        break;
+
+      case "link": {
+        const linkMark: Mark = {
+          type: "link",
+          attrs: {
+            href: node.url ?? "#",
+            target: "_blank",
+            rel: "noopener noreferrer",
+            class: null,
+          },
+        };
+        result.push(...convertInline(node.children, [...marks, linkMark]));
+        break;
+      }
+
+      case "image":
+        // Only HTTP/HTTPS images — local Obsidian paths are not resolvable here
+        if (typeof node.url === "string" && /^https?:\/\//.test(node.url)) {
+          result.push({
+            type: "image",
+            attrs: {
+              src: node.url,
+              alt: node.alt ?? null,
+              title: node.title ?? null,
+            },
+          });
+        }
+        break;
+
+      case "break":
+        result.push({ type: "hardBreak" });
+        break;
+
+      default:
+        // Try to extract content from unknown inline nodes
+        if (Array.isArray(node.children)) {
+          result.push(...convertInline(node.children, marks));
+        } else if (node.value) {
+          const n: TipTapNode = { type: "text", text: node.value as string };
+          if (marks.length) n.marks = marks;
+          result.push(n);
+        }
+    }
+  }
+
+  return result;
+}
+
+// ── Block converter ───────────────────────────────────────────────────────────
+
+function convertBlock(nodes: MdastNode[]): TipTapNode[] {
+  const result: TipTapNode[] = [];
+
+  for (const node of nodes) {
+    switch (node.type) {
+      case "paragraph": {
+        const content = convertInline(node.children ?? []);
+        result.push(content.length ? { type: "paragraph", content } : { type: "paragraph" });
+        break;
+      }
+
+      case "heading": {
+        const content = convertInline(node.children ?? []);
+        result.push({
+          type: "heading",
+          attrs: { level: node.depth ?? 2 },
+          content,
+        });
+        break;
+      }
+
+      case "blockquote": {
+        const content = convertBlock(node.children ?? []);
+        result.push({ type: "blockquote", content });
+        break;
+      }
+
+      case "code": {
+        result.push({
+          type: "codeBlock",
+          attrs: { language: node.lang ?? null },
+          content: [{ type: "text", text: node.value as string }],
+        });
+        break;
+      }
+
+      case "list": {
+        const listType = node.ordered ? "orderedList" : "bulletList";
+        const items = (node.children as MdastNode[]).map((item) => ({
+          type: "listItem",
+          content: convertBlock(item.children ?? []),
+        }));
+        const listNode: TipTapNode = { type: listType, content: items };
+        if (node.ordered) listNode.attrs = { start: (node.start as number) ?? 1 };
+        result.push(listNode);
+        break;
+      }
+
+      case "thematicBreak":
+        result.push({ type: "horizontalRule" });
+        break;
+
+      // Skip html, definitions, footnotes, etc.
+    }
+  }
+
+  return result;
+}
+
+// ── Public API ────────────────────────────────────────────────────────────────
+
+/**
+ * Converts a Markdown string to a TipTap/ProseMirror JSON document.
+ * Handles: headings, paragraphs, bold, italic, strike, inline code,
+ * code blocks, blockquotes, lists (nested), links, images (HTTP only),
+ * horizontal rules, hard breaks.
+ *
+ * Obsidian-specific syntax (![[wikilink]], [[link]]) is silently ignored
+ * since local file paths are not available during server-side import.
+ */
+export function mdToTiptap(markdown: string): object {
+  // Strip Obsidian wikilinks: [[link]] → plain text, ![[image]] → removed
+  const cleaned = markdown
+    .replace(/!\[\[([^\]]+)\]\]/g, "") // remove ![[image]] embeds
+    .replace(/\[\[([^\]|]+)(?:\|([^\]]+))?\]\]/g, (_m, target, alias) => alias ?? target); // [[link|alias]] → alias or target
+
+  const tree = unified().use(remarkParse).parse(cleaned);
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const content = convertBlock((tree as any).children ?? []);
+
+  if (content.length === 0) {
+    content.push({ type: "paragraph" });
+  }
+
+  return { type: "doc", content };
+}