(chore) add associate tasks

tasks/4.6-namespace-validation.md

@@ -0,0 +1,14 @@
+# 4.6 — Namespace/resource-name validation by snapshot membership (GREEN)
+
+Phase: 4 — Terminal (Surface C)
+Stage: GREEN
+
+Depends on: [4.2](4.2-exec-test.md), [1.7](1.7-dto-allowlist.md)
+
+- [ ] Namespace and resource-name arguments validated by **set membership against current snapshot**, not regex/escaping
+
+## Verify
+
+```bash
+go test ./... -run TestExec -v
+```