feat: shell controller, TabStage, layout and theme plugins with repair view

src/ui/look/resolve-look.ts

@@ -0,0 +1,49 @@
+import type { LookResponse } from "@/api/look-api";
+import { BUILTIN_LAYOUT_ID } from "./layout-registry";
+
+/** The theme a fresh install starts in when nothing else says otherwise. */
+export const FALLBACK_THEME = "dark";
+
+/**
+ * The layout to show: the user's choice, else the admin default, else the
+ * default look, else core's built-in. Without an answer from the server the
+ * last layout this browser showed stands in.
+ */
+export function resolveLayoutId(
+  look: LookResponse | null,
+  lastShown: string | null = null,
+): string {
+  if (!look) return lastShown ?? BUILTIN_LAYOUT_ID;
+  return (
+    look.layoutId ??
+    look.defaults.layout ??
+    look.defaultLook.layout ??
+    BUILTIN_LAYOUT_ID
+  );
+}
+
+/**
+ * The theme to show: the user's choice, else the one this browser kept
+ * (today's per-device setting, so existing users see no change), else the
+ * admin default, else the layout's own, else the default look's.
+ */
+export function resolveThemeId(
+  look: LookResponse | null,
+  localTheme: string | null,
+  layoutDefaultTheme?: string,
+): string {
+  return (
+    look?.themeId ??
+    localTheme ??
+    look?.defaults.theme ??
+    layoutDefaultTheme ??
+    look?.defaultLook.theme ??
+    FALLBACK_THEME
+  );
+}
+
+/** ?safe-layout=1 in the address bar opens the repair view. */
+export function safeLayoutInUrl(search: string): boolean {
+  const value = new URLSearchParams(search).get("safe-layout");
+  return value === "1" || value === "true";
+}