feat: add support for stat templates

Introduces a new `template` stat type that allows for table-based
lookups via CSV blocks in markdown files. When a template stat is
rolled, it uses a dice expression defined in the template to select
an entry, applies a label, and automatically updates associated
modifier stats using relative values.

src/cli/completions/index.ts

@@ -6,6 +6,7 @@ import { diceSource } from "./sources/dice.js";
 import { linksSource } from "./sources/links.js";
 import { sparkTablesSource } from "./sources/spark-tables.js";
 import { statsSource } from "./sources/stats.js";
+import { templatesSource } from "./sources/templates.js";
 import type { CompletionSource, CompletionsPayload } from "./types.js";
 
 export type {
@@ -14,6 +15,7 @@ export type {
   LinkCompletion,
   SparkTableCompletion,
   StatDef,
+  StatTemplate,
 } from "./types.js";
 
 /** Registered sources — open for extension */
@@ -22,6 +24,7 @@ const sources: CompletionSource[] = [
   linksSource,
   sparkTablesSource,
   statsSource,
+  templatesSource,
 ];
 
 /**