fix: enforce renderLimit for empty renderTemplates calls (#894)

renderLimit was only checked inside the per-template loop, so
renderTemplates([], ...) skipped it. Empty {% for %} and {% tablerow %}
bodies call that path once per iteration (tablerow still does emitter
work for <tr>/<td>), bypassing the documented time budget. Check the
limiter at renderTemplates entry before the loop.

Add regression tests for empty for-body and empty tablerow-body.

Co-authored-by: Cursor <[email protected]>

src/render/render.ts

@@ -15,6 +15,7 @@ export class Render {
     if (!emitter) {
       emitter = ctx.opts.keepOutputType ? new KeepingTypeEmitter() : new SimpleEmitter()
     }
+    ctx.renderLimit.check(getPerformance().now())
     const errors = []
     for (const tpl of templates) {
       ctx.renderLimit.check(getPerformance().now())