Read the cluster's operational posture level from the posture-current
ConfigMap at ceremony grant time. Derive ShellClass via
derive_shell_class() and stamp into the granted SessionScope.
- Normal posture (5) -> ShellClass::System
- Any DEFCON escalation -> ShellClass::Application
- Fail-closed: missing ConfigMap -> Lockdown -> Application
- posture_level_at_establishment stored for audit/breach comparison
Signed-off-by: Tyler King <tking@guildhouse.dev>
Signed-off-by: Tyler J King <tking727@gmail.com>