feat: add kitchen view command and parser skeleton (task 0003)

Cut the first complete thread through both layers with the smallest set
of node types.

@kitchen-md/core gains a pure, total `parse` returning a
`DocumentAST` of `{ frontmatter, blocks, diagnostics }`, built from a
minimal remark pipeline (remark-parse + remark-frontmatter) with an
internal translation layer to core's own types. This slice models
frontmatter passthrough, HeadingBlock, ParagraphBlock, and TextNode;
remark's mdast does not surface in the public API.

@kitchen-md/bin gains the `view` subcommand (commander) that reads a
file, calls `parse`, and passes the AST to a pure `render` that returns
an ANSI-styled string via chalk (auto-suppressed off a TTY). Frontmatter
prints as raw YAML followed by a separator, headings styled distinctly
by level, paragraphs as prose. A missing argument prints usage and a
missing/unreadable file a human-readable error, both exiting 1.

Richer blocks/inline plus raw fallbacks are task 0004; malformed
frontmatter diagnostics and the basic.md smoke test are task 0007.

packages/core/package.json

@@ -8,5 +8,11 @@
   },
   "scripts": {
     "test": "bun test"
+  },
+  "dependencies": {
+    "remark-frontmatter": "^5.0.0",
+    "remark-parse": "^11.0.0",
+    "unified": "^11.0.5",
+    "yaml": "^2.9.0"
   }
 }

packages/core/src/index.ts

@@ -1 +1,2 @@
-export {};
+export { parse } from "./parse.ts";
+export type * from "./types.ts";

packages/core/src/index_test.ts

@@ -1,18 +1,93 @@
-import { describe, test } from "bun:test";
+import { describe, expect, test } from "bun:test";
+
+import { parse } from "@kitchen-md/core";
 
 describe("parser", () => {
   describe("frontmatter", () => {
-    test.todo("parses frontmatter fields as-is");
-    test.todo("returns an empty object for empty frontmatter");
-    test.todo("returns an empty object when there is no frontmatter");
+    test("parses frontmatter fields as-is", () => {
+      const source =
+        "---\ntitle: Classic Pancakes\nservings: 4\ntags: [breakfast, quick]\n---\n\n# Classic Pancakes";
+
+      const result = parse(source);
+
+      expect(result.frontmatter).toEqual({
+        title: "Classic Pancakes",
+        servings: 4,
+        tags: ["breakfast", "quick"],
+      });
+    });
+    test("returns an empty object for empty frontmatter", () => {
+      const source = "---\n---\n\n# Title";
+
+      const result = parse(source);
+
+      expect(result.frontmatter).toEqual({});
+      expect(result.blocks).toContainEqual({
+        type: "heading",
+        level: 1,
+        children: [{ type: "text", value: "Title" }],
+      });
+      expect(result.diagnostics).toEqual([]);
+    });
+    test("returns an empty object when there is no frontmatter", () => {
+      const result = parse("# Title");
+
+      expect(result.frontmatter).toEqual({});
+      expect(result.diagnostics).toEqual([]);
+    });
     test.todo(
       "does not throw on malformed frontmatter: frontmatter is {}, body still parses, and an invalid-frontmatter diagnostic preserves the raw YAML",
     );
   });
 
   describe("blocks", () => {
-    test.todo("parses headings at every level (1-6)");
-    test.todo("parses paragraphs with typed inline nodes");
+    test("parses headings at every level (1-6)", () => {
+      const source = "# H1\n\n## H2\n\n### H3\n\n#### H4\n\n##### H5\n\n###### H6";
+
+      const result = parse(source);
+
+      expect(result).toEqual({
+        frontmatter: {},
+        blocks: [
+          { type: "heading", level: 1, children: [{ type: "text", value: "H1" }] },
+          { type: "heading", level: 2, children: [{ type: "text", value: "H2" }] },
+          { type: "heading", level: 3, children: [{ type: "text", value: "H3" }] },
+          { type: "heading", level: 4, children: [{ type: "text", value: "H4" }] },
+          { type: "heading", level: 5, children: [{ type: "text", value: "H5" }] },
+          { type: "heading", level: 6, children: [{ type: "text", value: "H6" }] },
+        ],
+        diagnostics: [],
+      });
+    });
+    test("keeps blocks flat and in document order (a heading is a sibling of the following paragraph)", () => {
+      const result = parse("# Batter\n\nSift the flour into a bowl.");
+
+      expect(result).toEqual({
+        frontmatter: {},
+        blocks: [
+          { type: "heading", level: 1, children: [{ type: "text", value: "Batter" }] },
+          {
+            type: "paragraph",
+            children: [{ type: "text", value: "Sift the flour into a bowl." }],
+          },
+        ],
+        diagnostics: [],
+      });
+    });
+    test("parses paragraphs with typed inline nodes", () => {
+      const result = parse("Hello world");
+
+      expect(result).toEqual({
+        frontmatter: {},
+        blocks: [
+          {
+            type: "paragraph",
+            children: [{ type: "text", value: "Hello world" }],
+          },
+        ],
+        diagnostics: [],
+      });
+    });
     test.todo("parses an ordered list");
     test.todo("parses an unordered list");
     test.todo("models a list item as a container wrapping a paragraph, not a bare inline array");

packages/core/src/parse.ts

@@ -0,0 +1,46 @@
+import type { PhrasingContent, Root, RootContent } from "mdast";
+import remarkFrontmatter from "remark-frontmatter";
+import remarkParse from "remark-parse";
+import { unified } from "unified";
+import { parse as parseYaml } from "yaml";
+import type { Block, DocumentAST, Frontmatter, InlineNode } from "./types.ts";
+
+const processor = unified().use(remarkParse).use(remarkFrontmatter);
+
+export function parse(input: string): DocumentAST {
+  const tree = processor.parse(input);
+  const frontmatter = extractFrontmatter(tree);
+  const blocks = tree.children.flatMap(translateBlock);
+  return { frontmatter, blocks, diagnostics: [] };
+}
+
+function extractFrontmatter(tree: Root): Frontmatter {
+  const yamlNode = tree.children.find((node) => node.type === "yaml");
+  if (!yamlNode) {
+    return {};
+  }
+  const data = parseYaml(yamlNode.value);
+  if (data !== null && typeof data === "object" && !Array.isArray(data)) {
+    return data as Frontmatter;
+  }
+  return {};
+}
+
+function translateBlock(node: RootContent): Block[] {
+  if (node.type === "heading") {
+    return [{ type: "heading", level: node.depth, children: translateInline(node.children) }];
+  }
+  if (node.type === "paragraph") {
+    return [{ type: "paragraph", children: translateInline(node.children) }];
+  }
+  return [];
+}
+
+function translateInline(nodes: PhrasingContent[]): InlineNode[] {
+  return nodes.flatMap((node) => {
+    if (node.type === "text") {
+      return [{ type: "text", value: node.value }];
+    }
+    return [];
+  });
+}

packages/core/src/types.ts

@@ -0,0 +1,48 @@
+// The public AST node and document types returned by parse.
+
+export type Frontmatter = Record<string, unknown>;
+
+export interface Point {
+  line: number;
+  column: number;
+  offset?: number;
+}
+
+export interface Position {
+  start: Point;
+  end: Point;
+}
+
+export interface Diagnostic {
+  severity: "warning";
+  code: string;
+  message: string;
+  source?: string;
+  position?: Position;
+}
+
+export interface TextNode {
+  type: "text";
+  value: string;
+}
+
+export type InlineNode = TextNode;
+
+export interface HeadingBlock {
+  type: "heading";
+  level: 1 | 2 | 3 | 4 | 5 | 6;
+  children: InlineNode[];
+}
+
+export interface ParagraphBlock {
+  type: "paragraph";
+  children: InlineNode[];
+}
+
+export type Block = HeadingBlock | ParagraphBlock;
+
+export interface DocumentAST {
+  frontmatter: Frontmatter;
+  blocks: Block[];
+  diagnostics: Diagnostic[];
+}