refactor: use hiccup instead of string concatenation in todomvc

Replace hand-built HTML strings with hiccup vectors rendered by a
minimal hiccup→HTML converter (example/todomvc/pocketbook/hiccup.cljs).
Supports CSS-style selectors (:div.class#id), attribute maps, void
elements, and nested children.

example/todomvc/pocketbook/hiccup.cljs

@@ -0,0 +1,68 @@
+(ns pocketbook.hiccup
+  "Minimal hiccup → HTML string renderer."
+  (:require [clojure.string :as str]))
+
+(def ^:private void-tags
+  #{"area" "base" "br" "col" "embed" "hr" "img" "input"
+    "link" "meta" "param" "source" "track" "wbr"})
+
+(defn- esc [s]
+  (-> (str s)
+      (str/replace "&" "&")
+      (str/replace "<" "&lt;")
+      (str/replace ">" "&gt;")
+      (str/replace "\"" "&quot;")))
+
+(defn- render-attrs [m]
+  (let [sb (js/Array.)]
+    (doseq [[k v] m]
+      (when (and (some? v) (not (false? v)))
+        (.push sb " ")
+        (.push sb (name k))
+        (when-not (true? v)
+          (.push sb "=\"")
+          (.push sb (esc (str v)))
+          (.push sb "\""))))
+    (.join sb "")))
+
+(defn- parse-tag
+  "Parse :div.foo.bar#baz → [\"div\" \"foo bar\" \"baz\"]."
+  [tag]
+  (let [full     (name tag)
+        id       (second (re-find #"#([^.#]+)" full))
+        no-id    (str/replace full #"#[^.#]+" "")
+        parts    (str/split no-id #"\.")
+        tag-name (if (seq (first parts)) (first parts) "div")
+        classes  (str/join " " (rest parts))]
+    [tag-name (when (seq classes) classes) id]))
+
+(deftype RawHTML [s])
+
+(defn raw
+  "Wrap a string to be emitted without HTML escaping."
+  [s]
+  (RawHTML. s))
+
+(defn html
+  "Convert a hiccup form to an HTML string."
+  [form]
+  (cond
+    (nil? form)              ""
+    (instance? RawHTML form) (.-s form)
+    (string? form)           (esc form)
+    (number? form)           (str form)
+    (seq? form)              (apply str (map html form))
+    (vector? form)
+    (let [[tag & rest] form
+          [tag-name tag-classes tag-id] (parse-tag tag)
+          [attrs children] (if (map? (first rest))
+                             [(first rest) (next rest)]
+                             [nil rest])
+          attrs (cond-> (or attrs {})
+                  tag-id      (assoc :id tag-id)
+                  tag-classes (update :class #(str tag-classes (when % (str " " %)))))
+          inner (apply str (map html children))]
+      (if (contains? void-tags tag-name)
+        (str "<" tag-name (render-attrs attrs) " />")
+        (str "<" tag-name (render-attrs attrs) ">" inner "</" tag-name ">")))
+    :else (esc (str form))))