docs(template-require-mandatory-role-attributes): document strict-mode {{input}} assumption (Copilot review)

In strict GJS/GTS, {{input}} could resolve to any imported identifier — not
just Ember's classic helper. We assume the classic helper (renders native
input); false-positive risk is low in practice because strict-mode authors
rarely use the mustache form at all. Document the assumption inline so
future readers don't need to re-derive the tradeoff.

Author: johanrd

lib/rules/template-require-mandatory-role-attributes.js

@@ -48,6 +48,13 @@ function getTagName(node) {
   }
   if (node?.type === 'GlimmerMustacheStatement' && node.path?.original === 'input') {
     // The classic `{{input}}` helper renders a native <input>.
+    //
+    // Caveat: in strict GJS/GTS mode, `{{input}}` is whatever was imported
+    // under the name `input` — it could be the classic helper (still renders
+    // native <input>) or some user-defined component. We assume the classic
+    // helper; the false-positive rate in practice is low because strict-mode
+    // authors rarely use `{{input}}` at all (idiomatic is <input> or
+    // <Input>), and when they do, it's almost always the imported built-in.
     return 'input';
   }
   return null;