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/power.nix

@@ -58,7 +58,7 @@ in
     # Instant menu path (user decision 2026-07-10): the threshold node is
     # group-writable for `users` so nomarchy-menu can echo live without
     # rebuild; this oneshot still owns boot + AC-replug re-apply. Prefer
-    # live theme-state.json under /home/*/.nomarchy so a menu change
+    # live state.json under /home/*/.nomarchy so a menu change
     # survives reboot before the next sys-rebuild bakes the Nix option.
     systemd.services.nomarchy-battery-charge-limit = lib.mkIf cfg.laptop {
       description = "Apply battery charge end threshold from state or config";
@@ -80,7 +80,7 @@ in
         # Baked generation default (empty = full charge / no cap).
         limit=${if cfg.batteryChargeLimit != null then toString cfg.batteryChargeLimit else ""}
         # Prefer the newest live state write (menu path, no rebuild yet).
-        for st in /home/*/.nomarchy/theme-state.json; do
+        for st in /home/*/.nomarchy/state.json; do
           [ -r "$st" ] || continue
           v=$(jq -r '.settings.power.batteryChargeLimit // empty' "$st" 2>/dev/null || true)
           case "$v" in