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.

templates/downstream/state.json

@@ -0,0 +1,61 @@
+{
+  "version": 1,
+  "name": "Boreal",
+  "slug": "boreal",
+  "mode": "dark",
+  "wallpaper": "",
+  "colors": {
+    "base": "#21272F",
+    "mantle": "#1A1F26",
+    "surface": "#303A46",
+    "overlay": "#404D5C",
+    "text": "#D3DAE0",
+    "subtext": "#97A3B2",
+    "muted": "#5E6A78",
+    "accent": "#B79BE8",
+    "accentAlt": "#86C7C0",
+    "good": "#A3CF88",
+    "warn": "#E6C384",
+    "bad": "#E2818A"
+  },
+  "border": {
+    "active": "accent",
+    "inactive": "overlay"
+  },
+  "ansi": [
+    "#2E3742",
+    "#E2818A",
+    "#A3CF88",
+    "#E6C384",
+    "#86A9E0",
+    "#B79BE8",
+    "#86C7C0",
+    "#D3DAE0",
+    "#5E6A78",
+    "#EC98A0",
+    "#B4DB9C",
+    "#EFCF98",
+    "#9DBBEC",
+    "#C6AEEF",
+    "#99D6CF",
+    "#E8EDF2"
+  ],
+  "fonts": {
+    "mono": "GeistMono Nerd Font",
+    "ui": "Inter",
+    "size": 11
+  },
+  "ui": {
+    "gapsIn": 6,
+    "gapsOut": 14,
+    "borderSize": 3,
+    "rounding": 12,
+    "iconSize": 44,
+    "activeOpacity": 1.0,
+    "inactiveOpacity": 0.93,
+    "terminalOpacity": 0.9,
+    "blur": true,
+    "shadow": true
+  },
+  "settings": {}
+}