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>

.github/workflows/ci.yml

@@ -34,5 +34,8 @@ jobs:
       - name: Tests
         working-directory: src-tauri
         run: cargo test --locked
-      - name: The first-run page's JavaScript
-        run: node --check ui/app.js
+      - name: The pages' JavaScript, and the script the content view runs
+        run: |
+          for f in ui/*.js src-tauri/src/*.js; do node --check "$f"; done
+      - name: The design tokens are the server's, as pinned
+        run: scripts/fetch-tokens.sh