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/nomarchy-install.sh

@@ -585,7 +585,7 @@ rm -rf /mnt/etc/nixos
 cp "$SHARE/template/flake.nix" \
    "$SHARE/template/system.nix" \
    "$SHARE/template/home.nix" \
-   "$SHARE/template/theme-state.json" \
+   "$SHARE/template/state.json" \
    "$FLAKE_DIR/"
 
 # Detected hardware → flags for the patcher (safe defaults active).
@@ -679,7 +679,7 @@ if (( compose_ok != 0 )); then
     (cd "$FLAKE_DIR" && nix --extra-experimental-features "nix-command flakes" flake lock)
 fi
 
-# A flake worktree must be git-tracked (theme-state.json especially).
+# A flake worktree must be git-tracked (state.json especially).
 (
     cd "$FLAKE_DIR"
     git init -q
@@ -702,7 +702,7 @@ success "Configuration written to ~$USERNAME/.nomarchy"
 section "Installing (this takes a while)"
 
 # Seed the target store with the flake source + all inputs so the first
-# `nomarchy-theme-sync apply` (and the HM pre-activation below) work
+# `nomarchy-state-sync apply` (and the HM pre-activation below) work
 # before the machine has ever seen a network. Two steps because
 # `flake archive --to` enforces signatures and locally-evaluated source
 # paths have none; plain `nix copy` accepts --no-check-sigs.