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.

pkgs/nomarchy-install/patch-template.py

@@ -116,7 +116,7 @@ def build_installer_region(v: dict) -> str:
     ]
 
     # Auto-login is deliberately NOT emitted here — it is seeded into
-    # theme-state.json instead (patch_state). A line in system.nix outranks
+    # state.json instead (patch_state). A line in system.nix outranks
     # the state default, which would make the System › Auto-login toggle
     # write JSON that nothing reads.
 
@@ -260,7 +260,7 @@ def patch_system(text: str, v: dict) -> str:
 
 
 def patch_state(text: str, v: dict) -> str:
-    """Seed menu-owned settings into theme-state.json.
+    """Seed menu-owned settings into state.json.
 
     These live in the state rather than system.nix precisely so the menu can
     change them later: a baked Nix assignment would outrank the state default
@@ -286,7 +286,7 @@ def main() -> None:
         "flake.nix": patch_flake,
         "home.nix": patch_home,
         "system.nix": patch_system,
-        "theme-state.json": patch_state,
+        "state.json": patch_state,
     }
     for name, fn in mapping.items():
         path = flake_dir / name