fix(journal): tokenize bare dice notation

The tokenizer only recognized dice when the pattern started with a count (3d6), so a bare d20 fell through to the identifier branch and failed as an unknown identifier. Add a dedicated branch for the bare d-form; DICE_RE already accepted it.

src/components/journal/variable-expression.ts

@@ -6,7 +6,7 @@
  *   - Number literals (integer or decimal)
  *   - Tagmap literals: #warrior:1;#druid:2 (bare #warrior → #warrior:1)
  *   - $var references (resolved via lookup; auto-detects number vs tagmap)
- *   - Dice patterns: 3d6, 2d8kh1, etc. (delegates to rollFormula)
+ *   - Dice patterns: 3d6, 2d8kh1, d20, etc. (delegates to rollFormula)
  *   - Arithmetic: + - * / (type-checked via registry)
  *   - Functions: floor(x), ceil(x), round(x) (numbers only)
  *   - Parentheses for grouping
@@ -225,6 +225,22 @@ function tokenize(input: string): Token[] {
       continue;
     }
 
+    // Dice pattern without a leading count: e.g. "d20", "d6kh1". The number
+    // branch above only catches dice that start with a digit ("3d6"), so bare
+    // forms need their own branch before the generic identifier branch.
+    if (/[dD]/.test(ch) && i + 1 < input.length && /[0-9]/.test(input[i + 1])) {
+      let dice = "";
+      while (i < input.length && /[a-zA-Z0-9]/.test(input[i])) {
+        dice += input[i];
+        i++;
+      }
+      if (!DICE_RE.test(dice)) {
+        throw new Error(`Invalid dice notation: "${dice}"`);
+      }
+      tokens.push({ kind: "number", value: String(rollDice(dice)), raw: dice });
+      continue;
+    }
+
     // Tagmap literal: #warrior:1;#druid:2 or bare #warrior
     if (ch === "#") {
       let raw = "";