The look from the server's tokens, pinned; the frame and bar follow the page's theme

ui/tokens.css is no longer a hand copy that drifts: scripts/fetch-tokens.sh
takes the server's tokens.css at a git ref and tokens.lock.json pins it, as
fetch-cli.sh does for the CLI. build.rs reads the two themes' --bg and --border
out of it, so no colour is written in Rust. The content view reports the page's
theme by a navigation the app refuses (llembas-theme:<name>), and the window,
the title bar and the first-run page are painted in it and remember it.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

ui/theme.js

@@ -0,0 +1,15 @@
+// The app's own pages are painted in the server page's theme, which the app reports in `status`
+// (see src-tauri/src/lib.rs: the content view says, the app remembers). tokens.css selects a
+// theme by `data-theme` and `data-base` on <html>, as the server's pages do; with nothing set
+// it is Moria, the server's own default, so the page needs no script to be right at first.
+"use strict"
+
+window.lembasTheme = {
+  apply(name) {
+    if (name !== "moria" && name !== "shire") return
+    const root = document.documentElement
+    if (root.dataset.theme === name) return
+    root.dataset.theme = name
+    root.dataset.base = name
+  },
+}