Exclude SECURITY.md + AGENTS.md from RAT

These scaffold files carry an SPDX license header, but this repo's Apache RAT
check doesn't scan headers embedded in Markdown, so list them in .rat-excludes.

Generated-by: Claude Code

Author: potiuk

.rat-excludes

@@ -3,3 +3,8 @@ go.mod
 go.sum
 rat-report.txt
 apache-rat-0.17
+
+# Security-model scaffold (carries an SPDX header; exempted
+# from RAT for setups that don't scan Markdown headers).
+AGENTS.md
+SECURITY.md