feat(theme): make Boreal the distro default

Seed theme-state.json and the downstream template from themes/boreal.json
(including border + empty settings). Point eval/schema fallbacks at Boreal
(theme.nix preset, plymouth and live-ISO splash colors, theme-shot, sync
error examples). Docs/TESTING and RECOVERY follow the new default.

Verified: state matches boreal palette; theme-contrast all pass.
preview.png for boreal still missing (picker plain-name; V3 capture).

modules/home/theme.nix

@@ -22,10 +22,10 @@ let
 
   # Defaults guarantee evaluation succeeds on a sparse or older state
   # file (e.g. one written before a schema field was added). The shipped
-  # Tokyo Night preset provides the color/ansi fallbacks; the path is
+  # Boreal preset provides the color/ansi fallbacks; the path is
   # relative to this module, so it resolves inside Nomarchy's own flake
   # source even when consumed downstream.
-  preset = builtins.fromJSON (builtins.readFile ../../themes/tokyo-night.json);
+  preset = builtins.fromJSON (builtins.readFile ../../themes/boreal.json);
 
   defaults = preset // {
     fonts = {
@@ -132,7 +132,7 @@ let
       ${toString cfg.stateFile} is a snapshot of it). The tool prints
       the same report with per-field fixes: `nomarchy-theme-sync
       validate`. Re-applying any preset resets all appearance fields:
-      `nomarchy-theme-sync apply tokyo-night`.'';
+      `nomarchy-theme-sync apply boreal`.'';
 
   # A border value is a palette key (look it up in colors) unless it's
   # already a literal hex; unknown keys fall through to the raw string.