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.

agent/HARDWARE-QUEUE.md

@@ -237,7 +237,7 @@ the **T14s** (webcam case).
       open Ghostty, so the hand `btop.theme` assets were only guest-file
       asserted (main_bg / inactive_fg keys) + desktop/bar rendered for
       rose-pine, everforest, summer-night, vantablack, catppuccin. On a
-      real session: `nomarchy-theme-sync apply <slug>` then `btop` and
+      real session: `nomarchy-state-sync apply <slug>` then `btop` and
       confirm backgrounds/text match the theme (esp. rose-pine Dawn light
       bg `#faf4ed`, vantablack near-black `#0d0d0d`, catppuccin Mocha
       `#1E1E2E`). One pass cycling those five is enough.