feat: add semantic CSS stylesheets (#3274)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

packages/pdf/src/semantic/public.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, it } from "vitest";
+import { inspectResumePdf } from "@reactive-resume/pdf/semantic";
+import { sampleResumeData } from "@reactive-resume/schema/resume/sample";
+
+describe("@reactive-resume/pdf/semantic", () => {
+	it("publicly exposes invalid applied-source diagnostics", () => {
+		const data = structuredClone(sampleResumeData);
+		const invalid = { languageVersion: 1, text: "@version 1; section { color: ; }" };
+		data.metadata.stylesheet = { mode: "semantic", source: invalid, applied: invalid };
+
+		const inspection = inspectResumePdf({ data });
+
+		expect(inspection.diagnostics).toContainEqual(expect.objectContaining({ severity: "error" }));
+		expect(inspection.presentation).toEqual({});
+	});
+});