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>

README.md

@@ -55,6 +55,7 @@ Needs Rust (stable) and, on Linux, WebKitGTK 4.1 and an AppIndicator library:
 ```sh
 sudo apt install libwebkit2gtk-4.1-dev libayatana-appindicator3-dev librsvg2-dev libxdo-dev
 scripts/fetch-cli.sh                 # the bundled CLI, checked against its release signature
+scripts/fetch-tokens.sh              # verifies ui/tokens.css against tokens.lock.json
 cargo install tauri-cli --version "^2" --locked
 cargo tauri dev                      # or: cargo tauri build
 ```
@@ -63,6 +64,13 @@ There is no Node and no bundler: the app's one local page is plain HTML, CSS and
 `ui/`. Everything else on screen is the server's own web UI. The version of the CLI it carries is
 in `lembas-cli.version`.
 
+Two files in `ui/` are generated and committed. `ui/tokens.css` is the server's design tokens,
+copied by `scripts/fetch-tokens.sh <server tag>` from a checkout of the server beside this
+repository (`../LLeMbas`, or `LEMBAS_SERVER`) and pinned in `tokens.lock.json`; run it with a
+new tag when the server's look changes. `ui/i18n.js` is the pages' words in the server's
+languages, written by `scripts/gen-i18n.py` from the server's catalogues and the script's own
+table; run it when a string on the page changes.
+
 ## Licence
 
 MIT; see [LICENSE](LICENSE). The bundled LLeMbas CLI is MIT too, with its own third-party notices.