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/yazi.nix

@@ -1,6 +1,6 @@
 # yazi — the flagship file manager: a fast, keyboard-driven TUI that
 # fits the distro's identity (Kitty graphics previews, rofi
-# menus, everything from one JSON). Themed from theme-state.json and
+# menus, everything from one JSON). Themed from state.json and
 # shipped with a curated plugin set. The GUI half (Thunar, "open folder"
 # handler) is nomarchy.system.fileManager on the system side.
 #