state: expose aids and use instance id as key

Fortify state store instances was specific to aids due to outdated design decisions carried over from the ego rewrite. That no longer makes sense in the current application, so the interface now enables a single store object to manage all transient state.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

test.nix

@@ -214,5 +214,8 @@ nixosTest {
     swaymsg("exit", succeed=False)
     machine.wait_until_fails("pgrep -x sway")
     machine.wait_for_file("/tmp/sway-exit-ok")
+
+    # Print fortify runDir contents:
+    print(machine.succeed("find /run/user/1000/fortify"))
   '';
 }