Add landing page for kjol, documentation

CLAUDE.md

@@ -70,9 +70,21 @@ GOOS=js GOARCH=wasm go -C go test -exec="node testdata/domexec.js" ./wasmruntime
 ```
 
 `webui` components that measure the page (Tooltip, Popover, Menu, Modal, DatePicker, Tutorial,
-AutoTable) are **controllers**: create them once alongside your signals, never inside a render
-closure. Floating panels share one positioning engine (`webui/position.go`, pure math, unit-tested
-natively) driven by the `Floating` controller (`webui/floating.go`).
+AutoTable, SignaturePad, AsyncCombobox) are **controllers**: create them once alongside your
+signals, never inside a render closure. Floating panels share one positioning engine
+(`webui/position.go`, pure math, unit-tested natively) driven by the `Floating` controller
+(`webui/floating.go`).
+
+**Theming / dark mode.** The kit is themed by **semantic tokens**, not by a `dark:` variant on
+every class: components say `bg-surface` / `border-line` / `text-ink` / `text-accent` and never
+name a colour, so a theme is ten CSS variables rather than four hundred class strings. The app
+must define them (see `webui.ThemeTokens` for the required set, and the example's `css/app.css`
+for a working pair) plus `@custom-variant dark (&:where(.dark, .dark *));` — the built-in `dark`
+variant is a `prefers-color-scheme` media query, which a site with its own switch cannot use.
+Only genuinely *coloured* things (an alert's red tint) carry `dark:` variants. `webui.Theme` is
+the controller (`Toggle`, `ThemeToggle`, `Init`); `webui.ThemeBootScript` goes in the document
+head **before** the stylesheet, or dark-mode users get a white flash until the wasm loads. It is
+the only JavaScript in a gowasm app.
 
 ### web/