docs: add implementation plan for ansible-arch reconciliation

Also folds in the dead handlers/main.yaml finding discovered while writing the plan.

docs/superpowers/specs/2026-07-28-ansible-reconciliation-design.md

@@ -105,6 +105,12 @@ single-value `name:` key the audit grep didn't match).
 **Minor cleanup:** remove the duplicate `docker` package entry from the
 `cs_student` role — `devops` already declares it.
 
+**Dead file found during planning:** `roles/common/handlers/` contains both
+`main.yml` and `main.yaml`. Ansible's role loader searches handler file
+extensions in a fixed order and stops at the first match, so `main.yml`
+(which already has `become: true`) is the only one ever loaded — `main.yaml`
+is dead and orphaned. Delete it.
+
 ## Verification
 
 - `ansible-playbook site.yml --check --diff` runs clean (no unexpected