Fix ERB expression compilation when code contains a heredoc

When an ERB output tag wraps code in parentheses and that code contains
a heredoc (e.g. `method_call <<~GRAPHQL, variables`), the closing
parenthesis must appear on its own line after the heredoc terminator.
Without this, the compiled Ruby is syntactically invalid.

Includes a snapshot test for the compiled output.

Co-authored-by: Amp <amp@ampcode.com>
Amp-Thread-ID: https://ampcode.com/threads/T-019c7333-8beb-715a-9183-8434cd5fb15a

Author: pinzonjulian

lib/reactionview/template/handlers/herb/herb.rb

@@ -66,7 +66,9 @@ def add_rails_expression(indicator, code, wrap_parentheses:)
                       end
 
               if wrap_parentheses
-                @src << "(" << code << ")"
+                @src << "(" << code
+                @src << "\n" if code.match?(/<<[~-]?\s*['"`]?\w/)
+                @src << ")"
               else
                 @src << " " << code
               end

test/snapshots/herb/template_handler_test/test_0029_heredoc_with_trailing_arguments_compiles_to_valid_Ruby_compiled_ffc55de9e7891578a81f0a2b0c1346a5.txt

@@ -0,0 +1,8 @@
+ @output_buffer.append=(method_call <<~GRAPHQL, variables
+  query {
+    field
+  }
+GRAPHQL
+);
+ @output_buffer.safe_append='
+'.freeze;@output_buffer

test/template/handlers/herb_test.rb

@@ -342,4 +342,17 @@ def @view_context.ui_badge(count, **_options)
     assert_compiled_snapshot(template)
     assert_evaluated_snapshot(template, ivars: { config: { key: "value" } })
   end
+
+  test "heredoc with trailing arguments compiles to valid Ruby" do
+    template = <<~ERB
+      <%= method_call <<~GRAPHQL, variables
+        query {
+          field
+        }
+      GRAPHQL
+      %>
+    ERB
+
+    assert_compiled_snapshot(template)
+  end
 end