[doc](security) Add threat model for scans

AGENTS.md

@@ -2,6 +2,10 @@
 
 This is the codebase for Apache Doris, an MPP OLAP database. It primarily consists of the Backend module BE (`be/`, execution and storage engine), the Frontend module FE (`fe/`, optimizer and transaction core), and the Cloud module (`cloud/`, storage-compute separation). Your basic development workflow is: modify code, build using standard procedures, add and run tests, and submit relevant changes.
 
+## Security Threat Model
+
+For security scans, vulnerability triage, security reviews, and changes involving authentication, authorization, network boundaries, external catalogs, cloud tenancy, or other security-sensitive behavior, read `threat-model.md` first. Use it to determine in-scope components, trust boundaries, attacker roles, explicit non-goals, and triage classification. Findings that are out of model or by design under `threat-model.md` should be reported as such, not treated as Doris vulnerabilities.
+
 ## When running in a WORKTREE directory
 
 To ensure smooth test execution without interference between worktrees, the first thing to do upon entering a worktree directory is to check if `.worktree_initialized` exists. If not, execute `hooks/setup_worktree.sh`, setting `$ROOT_WORKSPACE_PATH` to the base directory (typically `${DORIS_REPO}`) beforehand. After successful execution, verify that `.worktree_initialized` has been touched and that `thirdparty/installed` dependencies exist correctly. Also check if submodules have been properly initialized; if not, do so manually.