docs(reference): cover bare dice and tilde fences

Add the bare d-form (d20) to the dice notation table, and note that role fences accept backticks or tildes with hyphen-capable attribute keys. Regenerate both reference copies from known.ts and mirror the notes in the skill and markdown docs.

src/cli/validate/known.ts

@@ -272,6 +272,7 @@ export interface DiceNotation {
 export const DICE_NOTATION: readonly DiceNotation[] = [
   { notation: "2d6", meaning: "two six-sided dice" },
   { notation: "1d20+5", meaning: "d20 plus modifier" },
+  { notation: "d20", meaning: "one twenty-sided die (count optional)" },
   { notation: "3d6kh1", meaning: "keep highest 1" },
   { notation: "3d6dl2-1", meaning: "drop lowest 2, minus 1" },
   { notation: "{d4, d8}", meaning: "choose one of the listed dice" },

src/cli/validate/reference.ts

@@ -151,6 +151,14 @@ export function renderReference(): string {
   );
   lines.push("handled.");
   lines.push("");
+  lines.push(
+    "Fences may use backticks or tildes (`~~~`); the closing fence must reuse",
+  );
+  lines.push(
+    "the opening marker. Fence attribute keys may contain hyphens (e.g.",
+  );
+  lines.push("`data-foo=bar`).");
+  lines.push("");
   for (const role of ROLE_SPECS) {
     lines.push(`### \`role=${role.role}\``);
     lines.push("");