docs: rework template and add stages framework

docs/template.typ

@@ -1,12 +1,47 @@
+// would also be interesting to try out IBM Plex Mono/Sans sometime
+#let atk = "Atkinson Hyperlegible"
+#let fonts = (
+	main: (font: atk, size: 12pt),
+
+	title: (font: atk, size: 20pt),
+	subtitle: (font: atk, size: 10pt),
+	heading: (font: "Montserrat", weight: "regular"),
+)
+
 #let conf(
-	doc
+	title: none,
+	subtitle: none,
+	doc,
 ) = {
-	set text(font: "Atkinson Hyperlegible");
-	show heading: it => [
-		#set text(font: "Montserrat", weight: "regular")
+	set page(
+		numbering: "1 / 1",
+		header: locate(loc => {
+			datetime.today().display()
 
-		#it
-	]
+			if counter(page).at(loc).first() > 1 {
+				// on all pages other than the first, the title is useful to have at hand
+				h(1fr)
+				title
+			}
+		}),
+	)
+	set text(..fonts.main)
+	set heading(numbering: "A.1")
 
+	show heading: it => text(..fonts.heading, it)
+
+	// document title
+	if title != none {
+		align(
+			right,
+			text(..fonts.title, title)
+			+ v(-12pt)
+			+ text(..fonts.subtitle, subtitle)
+		)
+
+		v(0.25cm)
+	}
+
+	// content itself
 	doc
 }