feat: add tags workflow

src/frontmatter/frontmatterFields.test.ts

@@ -1,11 +1,17 @@
 import { describe, expect, it } from "vitest";
-import { findFieldRange, replaceFrontmatterField } from "./frontmatterFields";
+import {
+	findFieldRange,
+	formatTagsYamlValue,
+	replaceFrontmatterField,
+	setFrontmatterTags,
+} from "./frontmatterFields";
 
 const sample = `---
 id: abc
 title: Hello
 status: todo
 priority: medium
+tags: [old]
 ---
 
 Body
@@ -47,3 +53,26 @@ describe("findFieldRange", () => {
 		expect(line.slice(range!.startCol, range!.endCol)).toBe("todo");
 	});
 });
+
+describe("formatTagsYamlValue", () => {
+	it("formats empty and simple lists", () => {
+		expect(formatTagsYamlValue([])).toBe("[]");
+		expect(formatTagsYamlValue(["bug", "frontend"])).toBe(
+			"[bug, frontend]",
+		);
+	});
+
+	it("quotes tags with spaces", () => {
+		expect(formatTagsYamlValue(["my tag"])).toBe('["my tag"]');
+	});
+});
+
+describe("setFrontmatterTags", () => {
+	it("replaces the tags line", () => {
+		const result = setFrontmatterTags(sample, ["bug", "docs"]);
+		expect(result.ok).toBe(true);
+		if (!result.ok) return;
+		expect(result.content).toContain("tags: [bug, docs]");
+		expect(result.content).not.toContain("tags: [old]");
+	});
+});