perf: render template in a single pass

Replace the per-variable loop (each iteration building a fresh RegExp
and scanning the full template) with one pass over TOKEN_REGEX that
substitutes every token inline. Fewer allocations and O(n) in template
length instead of O(n * number of variables). Unknown tokens are left
untouched, matching the previous behavior.

Author: bug3

src/renderer.ts

@@ -1,11 +1,7 @@
-export function render(template: string, values: Record<string, string>): string {
-    let result = template;
-
-    for (const [key, value] of Object.entries(values)) {
-        const escaped = key.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
-        const pattern = new RegExp(`\\{\\{${escaped}\\}\\}`, 'g');
-        result = result.replace(pattern, () => value);
-    }
+const TOKEN_REGEX = /\{\{([a-zA-Z_][a-zA-Z0-9_]*)\}\}/g;
 
-    return result;
+export function render(template: string, values: Record<string, string>): string {
+    return template.replace(TOKEN_REGEX, (match, key) => (
+        Object.hasOwn(values, key) ? values[key] : match
+    ));
 }