chore: scaffold Bun workspace monorepo

Sets up the initial project structure: two packages (@kitchen-md/core
and @kitchen-md/bin), shared tsconfig, shared fixtures, per-package
test stubs (unit, integration, smoke), .gitignore, and project
CLAUDE.md with Conventional Commits convention.

packages/core/src/index.ts

@@ -0,0 +1 @@
+export {};

packages/core/src/index_test.ts

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+import { describe, test } from "bun:test";
+
+describe("parser", () => {
+  test.todo("parses frontmatter fields as-is");
+  test.todo("extracts ingredient name, quantity, and unit");
+  test.todo("extracts ingredient without unit");
+  test.todo("extracts multi-word ingredient name");
+  test.todo("extracts cookware without quantity");
+  test.todo("extracts cookware with quantity");
+  test.todo("extracts multi-word cookware name");
+  test.todo("extracts timer as single value");
+  test.todo("extracts timer as range");
+  test.todo("annotations embedded mid-sentence are captured");
+  test.todo("standard Markdown elements pass through without interference");
+});

packages/core/src/integration_test.ts

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+import { describe, test } from "bun:test";
+
+describe("parser — integration", () => {
+  test.todo("parses the primary fixture and extracts all annotations");
+});