docs(memory): record that Entra group member reads hide service principals

az ad group member list and GET /groups/{id}/members return an empty
collection, without error, for groups whose members are service principals.
Records the reads that do work and the rule to trust a Terraform plan over
that output.

home/claude/memory/MEMORY.md

@@ -16,3 +16,4 @@
 - [Nix shell tooling](nix_shell_tooling.md) — any nixpkgs tool runs ad hoc via `nix run`/`nix shell nixpkgs#<pkg>`; a missing command is never a dead end
 - [WSP local build and test](wsp_local_build_and_test.md) — core-services-cloud on this box: dotnet via nix, artifactory creds from `~/.artifactoryenv` sourced per command, how to tell auth failure from a code failure
 - [WSP-32957 PIM migration](wsp_32957_pim_migration.md) — AKS RBAC to PIM + AutoPerm decommission; prod is in the Technical Preview subscription, three tenants; resume via `~/code/WSP-32957-CONTINUATION.md`
+- [Entra group member reads](entra_group_member_reads.md) — `az ad group member list` hides service principal members; use the servicePrincipal cast or transitiveMemberOf, and trust the Terraform plan over it