feat: add 13 components adapted from Oat UI

Components (.cljc + .css + tests):
- Alert (success/warning/danger/info variants)
- Badge (primary/secondary/outline/success/warning/danger)
- Card (card/card-header/card-body/card-footer)
- Accordion (collapsible with open/closed state)
- Table (headers/rows, striped/bordered variants)
- Dialog (modal with header/body/footer sections)
- Breadcrumb (nav with active item)
- Pagination (current/total with prev/next)
- Progress (value bar with color variants)
- Spinner (sm/md/lg sizes)
- Skeleton (line/box/circle/heading placeholders)
- Switch (toggle with checked/disabled states)
- Tooltip (hover text via data-tooltip attr)

CSS-only additions:
- Form elements (inputs, selects, checkboxes, radios, range, groups)
- Grid (12-column system with offsets, responsive)
- Utilities (flex, spacing, alignment, sr-only)

Also adds warning/fg-on-warning tokens to light and dark themes.
All 3 dev targets updated with full component showcase.
40 tests, 213 assertions, all passing.

src/ui/skeleton.cljc

@@ -0,0 +1,44 @@
+(ns ui.skeleton
+  (:require [clojure.string :as str]))
+
+#?(:squint (defn- kw-name [s] s)
+   :cljs   (defn- kw-name [s] (name s))
+   :clj    (defn- kw-name [s] (name s)))
+
+(defn skeleton-class-list
+  "Generate a vector of CSS class strings for a skeleton placeholder.
+   Variants: :line (text line), :box (square), :circle, :heading."
+  [{:keys [variant]}]
+  (cond-> ["skeleton"]
+    variant (conj (str "skeleton--" (kw-name variant)))))
+
+(defn skeleton-classes
+  "Generate CSS class string for a skeleton."
+  [opts]
+  (str/join " " (skeleton-class-list opts)))
+
+(defn skeleton
+  "Render a skeleton loading placeholder.
+
+   Props:
+     :variant - :line, :box, :circle, :heading
+     :class   - additional CSS classes
+     :attrs   - additional HTML attributes"
+  [{:keys [variant class attrs] :as _props}]
+  #?(:squint
+     (let [classes (cond-> (skeleton-classes {:variant variant})
+                     class (str " " class))
+           base-attrs (merge {:class classes :role "status" :aria-label "Loading"} attrs)]
+       [:div base-attrs])
+
+     :cljs
+     (let [cls (skeleton-class-list {:variant variant})
+           classes (cond-> cls class (conj class))
+           base-attrs (merge {:class classes :role "status" :aria-label "Loading"} attrs)]
+       [:div base-attrs])
+
+     :clj
+     (let [classes (cond-> (skeleton-classes {:variant variant})
+                     class (str " " class))
+           base-attrs (merge {:class classes :role "status" :aria-label "Loading"} attrs)]
+       [:div base-attrs])))