Add update/hydrate methods and browser auto-init to sexp.js

Adds Sexp.update() for re-rendering data-sexp elements with new data,
Sexp.hydrate() for finding and rendering all [data-sexp] elements,
and auto-init on DOMContentLoaded + htmx:afterSwap integration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/static/scripts/sexp.js

@@ -1189,6 +1189,49 @@
       }
     },
 
+    /**
+     * Bind client-side sexp rendering to elements with data-sexp-* attrs.
+     *
+     * Pattern:
+     *   <div data-sexp="(~card :title title)" data-sexp-env='{"title":"Hi"}'>
+     *     <!-- server-rendered HTML (hydration target) -->
+     *   </div>
+     *
+     * Call Sexp.update(el, {title: "New"}) to re-render with new data.
+     */
+    update: function (target, newEnv) {
+      var el = typeof target === "string" ? document.querySelector(target) : target;
+      if (!el) return;
+      var source = el.getAttribute("data-sexp");
+      if (!source) return;
+      var baseEnv = {};
+      var envAttr = el.getAttribute("data-sexp-env");
+      if (envAttr) {
+        try { baseEnv = JSON.parse(envAttr); } catch (e) { /* ignore */ }
+      }
+      var env = merge({}, _componentEnv, baseEnv, newEnv || {});
+      var node = renderDOM(parse(source), env);
+      el.textContent = "";
+      el.appendChild(node);
+      if (newEnv) {
+        merge(baseEnv, newEnv);
+        el.setAttribute("data-sexp-env", JSON.stringify(baseEnv));
+      }
+    },
+
+    /**
+     * Find all [data-sexp] elements within root and render them.
+     * Useful after HTMX swaps bring in new sexp-enabled elements.
+     */
+    hydrate: function (root) {
+      var els = (root || document).querySelectorAll("[data-sexp]");
+      for (var i = 0; i < els.length; i++) {
+        if (els[i]._sexpHydrated) continue;
+        els[i]._sexpHydrated = true;
+        Sexp.update(els[i]);
+      }
+    },
+
     // For testing
     _types: { NIL: NIL, Symbol: Symbol, Keyword: Keyword, Lambda: Lambda, Component: Component, RawHTML: RawHTML },
     _eval: sexpEval,
@@ -1203,17 +1246,20 @@
   // =========================================================================
 
   if (typeof document !== "undefined") {
-    // Process sexp scripts on DOMContentLoaded
-    function init() { Sexp.processScripts(); }
+    var init = function () {
+      Sexp.processScripts();
+      Sexp.hydrate();
+    };
     if (document.readyState === "loading") {
       document.addEventListener("DOMContentLoaded", init);
     } else {
       init();
     }
 
-    // Re-process after HTMX swaps (new sexp scripts may have arrived)
+    // Re-process after HTMX swaps
     document.addEventListener("htmx:afterSwap", function (e) {
       Sexp.processScripts(e.detail.target);
+      Sexp.hydrate(e.detail.target);
     });
   }