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/home/autotheme.nix

@@ -1,5 +1,5 @@
 # Auto time-of-day theme switch (BACKLOG #79, VISION § D). A user timer
-# periodically runs `nomarchy-theme-sync auto`, which reads
+# periodically runs `nomarchy-state-sync auto`, which reads
 # settings.autoTheme = { enable, day, night, sunrise, sunset } from the
 # state file and applies the day or night preset for the current clock —
 # through the SAME one engine as a manual `apply` (no second pipeline).
@@ -20,7 +20,7 @@ lib.mkIf (config.nomarchy.settings.autoTheme.enable or false) {
       # The rebuild (`home-manager switch`) and its tools resolve from the
       # system + per-user profiles — same PATH shape nomarchy-updates uses.
       Environment = "PATH=/run/current-system/sw/bin:/etc/profiles/per-user/${config.home.username}/bin";
-      ExecStart = "${pkgs.nomarchy-theme-sync}/bin/nomarchy-theme-sync auto";
+      ExecStart = "${pkgs.nomarchy-state-sync}/bin/nomarchy-state-sync auto";
     };
   };