refactor(#107): theme-state.json → state.json, theme-sync → state-sync

The machine flake's git-tracked settings file is system state, not
"theme" only — rename it to state.json. CLI becomes nomarchy-state-sync
with a nomarchy-theme-sync symlink for scripts and muscle memory.

Eval (mkFlake, doctor, lifecycle) still accepts theme-state.json; the
next write migrates to state.json and removes the legacy file.
Documented in MIGRATION.md; drop the CLI alias after release notes.

modules/nixos/services.nix

@@ -11,11 +11,11 @@ let
   # Control Center's Printing toggle writes settings.printing.enable; read it
   # from the state file, the only place it exists on the NixOS side (the
   # hardware.nix/timezone.nix bridge). Missing/invalid JSON fails closed via
-  # theme-state-read.nix rather than a raw stack. null = key absent, which
+  # state-read.nix rather than a raw stack. null = key absent, which
   # leaves the option's own default alone.
   svcState =
     if config.nomarchy.system.stateFile != null
-    then import ../theme-state-read.nix { inherit lib; } config.nomarchy.system.stateFile
+    then import ../state-read.nix { inherit lib; } config.nomarchy.system.stateFile
     else { };
   statePrinting =
     let v = (svcState.settings or { }).printing.enable or null;
@@ -97,7 +97,7 @@ in
       System ▸ Printers entry opens the system-config-printer GUI'' // {
       default = false;
       defaultText = lib.literalExpression
-        "(settings.printing.enable from theme-state.json) or false";
+        "(settings.printing.enable from state.json) or false";
     };
 
     openrgb.enable = lib.mkEnableOption ''