Send all responses as sexp wire format with client-side rendering

- Server sends sexp source text, client (sexp.js) renders everything
- SexpExpr marker class for nested sexp composition in serialize()
- sexp_page() HTML shell with data-mount="body" for full page loads
- sexp_response() returns text/sexp for OOB/partial responses
- ~app-body layout component replaces ~app-layout (no raw!)
- ~rich-text is the only component using raw! (for CMS HTML content)
- Fragment endpoints return text/sexp, auto-wrapped in SexpExpr
- All _*_html() helpers converted to _*_sexp() returning sexp source
- Head auto-hoist: sexp.js moves meta/title/link/script[ld+json]
  from rendered body to document.head automatically
- Unknown components render warning box instead of crashing page
- Component kwargs preserve AST for lazy rendering (fixes <> in kwargs)
- Fix unterminated paren in events/sexp/tickets.sexpr

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

shared/sexp/tests/test_sexp_js.py

@@ -203,3 +203,31 @@ class TestPythonParity:
         py_html = py_render(parse(call_text), env)
         js_html = _js_render(call_text, comp_text)
         assert js_html == py_html
+
+    MAP_CASES = [
+        # map with lambda returning HTML element
+        (
+            "",
+            '(ul (map (lambda (x) (li x)) ("a" "b" "c")))',
+        ),
+        # map with lambda returning component
+        (
+            '(defcomp ~item (&key name) (span :class "item" name))',
+            '(div (map (lambda (t) (~item :name (get t "name"))) ({"name" "Alice"} {"name" "Bob"})))',
+        ),
+        # map-indexed with lambda
+        (
+            "",
+            '(ul (map-indexed (lambda (i x) (li (str i ". " x))) ("foo" "bar")))',
+        ),
+    ]
+
+    @pytest.mark.parametrize("comp_text,call_text", MAP_CASES)
+    def test_map_lambda_render(self, comp_text, call_text):
+        env = {}
+        if comp_text:
+            for expr in parse_all(comp_text):
+                evaluate(expr, env)
+        py_html = py_render(parse(call_text), env)
+        js_html = _js_render(call_text, comp_text)
+        assert js_html == py_html, f"Mismatch:\n  PY: {py_html!r}\n  JS: {js_html!r}"