fix: align builtin aggregate template with runtime input shape

Addresses codex-review feedback: bundled aggregate_report rules are
evaluated with entries under input.aggregates_internal["cat/name"],
not the custom-rule compatibility shape input.aggregate. The prior
builtin template would produce a rule whose scaffolded test passed
(because it injected input.aggregate directly) but which never emitted
violations during normal linting.

Switch the builtin template to read from input.aggregates_internal
keyed by "{{.Category}}/{{.NameOriginal}}" and update the generated
test to exercise the same shape via util.with_source_files.

Author: mvanhorn

internal/embeds/templates/builtin/builtin_aggregate.rego.tpl

@@ -25,9 +25,10 @@ aggregate contains entry if {
 # schemas:
 #   - input: schema.regal.aggregate
 aggregate_report contains violation if {
-	# Correlate the collected entries across modules and emit a violation.
+	# Built-in aggregate rules read the collected entries from
+	# input.aggregates_internal, keyed by "category/name".
 	# Replace this example with your own cross-module condition.
-	some entry in input.aggregate
+	some entry in input.aggregates_internal["{{.Category}}/{{.NameOriginal}}"][_]
 
 	violation := result.fail(rego.metadata.chain(), entry.aggregate_source)
 }

internal/embeds/templates/builtin/builtin_aggregate_test.rego.tpl

@@ -1,14 +1,18 @@
 package regal.rules.{{.Category}}{{.NameTest}}
 
 import data.regal.ast
+import data.regal.util
 
 import data.regal.rules.{{.Category}}{{.Name}} as rule
 
 # Example test, replace with your own
 test_aggregate_reports_violation if {
 	agg := rule.aggregate with input as ast.policy("foo := true")
 
-	r := rule.aggregate_report with input.aggregate as agg
+	r := rule.aggregate_report with input.aggregates_internal as util.with_source_files(
+		"{{.Category}}/{{.NameOriginal}}",
+		[agg],
+	)
 
 	# Use print(r) here to see the report. Great for development!