Add typography roles, text primitives, fontkit measurer and layout lint

Txt always sets an absolute line height; RenderTxt never does. Row pins
every cell and stacks when the fill column would be too narrow. IdText and
FitText shrink then chunk or truncate. The fontkit measurer matches react-pdf
text widths exactly. A TypeScript-AST lint test enforces the layout rules
(no lineHeight outside Txt, no non-literal fixed/wrap/minPresenceAhead,
flexGrow needs flexBasis, no stray absolute positioning).

src/pdf/fonts/register.ts

@@ -1,17 +1,8 @@
 import { Font } from "@react-pdf/renderer";
 import { FONT_MANIFEST } from "./manifest";
+import { familySources } from "./stack";
 
-/** Every stack ends here: Latin and the rupee sign from Plex, then the Indic scripts. */
-export const FONT_STACK: readonly string[] = [
-  "IBM Plex Sans",
-  "Noto Sans Devanagari",
-  "Noto Sans Kannada",
-];
-
-/** `[primary, ...tail]` without duplicates, for a style's fontFamily. */
-export function stack(primary: string): string[] {
-  return [primary, ...FONT_STACK.filter((f) => f !== primary)];
-}
+export { FONT_STACK, familySources, stack, type FamilySource } from "./stack";
 
 let registered = false;
 
@@ -28,23 +19,11 @@ export function registerBundledFonts(base: string): void {
   registered = true;
 
   for (const fam of FONT_MANIFEST.families) {
-    const sources: { src: string; fontWeight: number; fontStyle: "normal" | "italic" }[] = [];
-    const weights = new Set<number>();
-    for (const font of fam.fonts) {
-      weights.add(font.weight);
-      sources.push({
-        src: `${base}/${fam.folder}/${font.file}`,
-        fontWeight: font.weight,
-        fontStyle: font.style,
-      });
-    }
-    // react-pdf resolves every family in a fallback stack with the node's own style and throws for
-    // a family that has no italic, so any weight without a real italic reuses its upright file.
-    for (const weight of weights) {
-      if (sources.some((s) => s.fontWeight === weight && s.fontStyle === "italic")) continue;
-      const upright = sources.find((s) => s.fontWeight === weight && s.fontStyle === "normal");
-      if (upright) sources.push({ ...upright, fontStyle: "italic" });
-    }
+    const sources = familySources(fam).map((s) => ({
+      src: `${base}/${fam.folder}/${s.file}`,
+      fontWeight: s.fontWeight,
+      fontStyle: s.fontStyle,
+    }));
     Font.register({ family: fam.family, fonts: sources });
   }