fix(bootstrap): target only remaining system (tsys-siem) [#403]

Access validation shows 68/70 non-excluded systems at intended access
state. Strip already-bootstrapped systems (devbox-cloudron, subopi3,
subopi-dev-3/4, ultix-field, pfvsvrpi, sectestbed-cloudron) from the
active list; tsys-siem is the sole remaining actionable target.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

WORKING.md

@@ -7,9 +7,6 @@ A commit is blocked while any task below remains unchecked.
 
 (all done — session complete)
 
-- [x] Wire guest-agent-as-access ban: strip vm-guest from remote.sh, add check-rules.sh rule #11, codify in AGENTS.md [#403]
-- [x] Convert vm-validation.sh + perf-matrix.sh + deploy-tuned-guests.sh from guest-agent to SSH
-- [x] Rewrite bootstrap-all.sh for remaining 8 locked-out systems
-- [x] Ban harness question-tool in meta (TSYSGroupAIOS) + project AGENTS.md
-- [x] Update Redmine #403 + Discourse #298 audit log
-- [x] Final access probe: 63/67 SSH+sudo working; 3 blocked on unrelated work
+- [x] Add NON-NEGOTIABLE session-start check-for-understanding gate to AGENTS.md
+- [x] Run full end-to-end access validation (68/70 non-excluded at intended state)
+- [x] Update bootstrap-all.sh to target only remaining system (tsys-siem) [#403]