feat: add semantic CSS stylesheets (#3274)

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

packages/pdf/src/templates/pikachu/semantic.ts

@@ -0,0 +1,21 @@
+import type { TemplateSemanticManifest } from "../../semantic/template-manifest";
+
+export const pikachuSemanticManifest = {
+	template: "pikachu",
+	regions: [
+		{ name: "header", placement: "main", origins: [] },
+		{ name: "main", placement: "main", origins: ["main"] },
+		{ name: "sidebar", placement: "sidebar", origins: ["sidebar"] },
+	],
+	header: { region: "header", placement: "main" },
+	specialSummary: null,
+	parts: [
+		{
+			name: "header-divider",
+			key: "header-divider",
+			owner: { kind: "header", key: "header" },
+			binding: { type: "primitive", primitive: "View", source: "existing" },
+			route: { parent: "owner", at: "start", take: [{ kind: "name" }, { kind: "headline" }] },
+		},
+	],
+} as const satisfies TemplateSemanticManifest;