add 20 browser API builtins to JS runtime and codegen preamble

Iteration 3: closes the browser API gap needed for real web pages.

New builtins in el_runtime.js:
  Extended DOM: dom_set_attr, dom_get_attr, dom_remove_attr, dom_set_html,
    dom_get_html, dom_get_parent, dom_contains_class, dom_get_checked,
    dom_set_checked
  Timers: set_timeout, set_interval, clear_interval
  Local storage: local_storage_get, local_storage_set, local_storage_remove
  Window: window_location, window_redirect, window_on_load
  Debug: console_log

All browser-only functions use _ensureBrowser guard. Timer functions
work in both Node and browser. All new names added to __el export
object, ES named exports, and codegen-js.el destructure preamble.
Spec table updated to document new categories.

el-compiler/runtime/el_runtime.js

@@ -630,6 +630,120 @@ function dom_is_null(el) {
     return el === null || el === undefined;
 }
 
+// ── Extended DOM API (browser-only) ───────────────────────────────────────
+
+function dom_set_attr(el, attr, val) {
+    _ensureBrowser('dom_set_attr');
+    if (el != null) el.setAttribute(String(attr), String(val));
+}
+
+function dom_get_attr(el, attr) {
+    _ensureBrowser('dom_get_attr');
+    if (el == null) return '';
+    return el.getAttribute(String(attr)) ?? '';
+}
+
+function dom_remove_attr(el, attr) {
+    _ensureBrowser('dom_remove_attr');
+    if (el != null) el.removeAttribute(String(attr));
+}
+
+function dom_set_html(el, html) {
+    _ensureBrowser('dom_set_html');
+    if (el != null) el.innerHTML = String(html);
+}
+
+function dom_get_html(el) {
+    _ensureBrowser('dom_get_html');
+    return el == null ? '' : String(el.innerHTML ?? '');
+}
+
+function dom_get_parent(el) {
+    _ensureBrowser('dom_get_parent');
+    return el == null ? null : (el.parentElement ?? null);
+}
+
+function dom_contains_class(el, cls) {
+    _ensureBrowser('dom_contains_class');
+    if (el == null) return false;
+    return el.classList.contains(String(cls));
+}
+
+function dom_get_checked(el) {
+    _ensureBrowser('dom_get_checked');
+    return el == null ? false : Boolean(el.checked);
+}
+
+function dom_set_checked(el, val) {
+    _ensureBrowser('dom_set_checked');
+    if (el != null) el.checked = Boolean(val);
+}
+
+// ── Timer API (browser + Node) ─────────────────────────────────────────────
+
+function set_timeout(ms, cb) {
+    if (typeof setTimeout === 'undefined') {
+        throw new Error('set_timeout: setTimeout not available in this environment');
+    }
+    setTimeout(cb, ms | 0);
+}
+
+function set_interval(ms, cb) {
+    if (typeof setInterval === 'undefined') {
+        throw new Error('set_interval: setInterval not available in this environment');
+    }
+    return setInterval(cb, ms | 0);
+}
+
+function clear_interval(handle) {
+    if (typeof clearInterval !== 'undefined') clearInterval(handle);
+}
+
+// ── Local storage (browser-only) ───────────────────────────────────────────
+
+function local_storage_get(key) {
+    _ensureBrowser('local_storage_get');
+    return localStorage.getItem(String(key)) ?? '';
+}
+
+function local_storage_set(key, val) {
+    _ensureBrowser('local_storage_set');
+    localStorage.setItem(String(key), String(val));
+}
+
+function local_storage_remove(key) {
+    _ensureBrowser('local_storage_remove');
+    localStorage.removeItem(String(key));
+}
+
+// ── Window location / navigation (browser-only) ────────────────────────────
+
+function window_location() {
+    _ensureBrowser('window_location');
+    return window.location.href;
+}
+
+function window_redirect(url) {
+    _ensureBrowser('window_redirect');
+    window.location.href = String(url);
+}
+
+function window_on_load(cb) {
+    if (typeof document !== 'undefined') {
+        document.addEventListener('DOMContentLoaded', cb);
+    } else if (typeof window !== 'undefined') {
+        window.addEventListener('load', cb);
+    }
+    // In Node: no-op
+}
+
+// ── console_log (explicit debug log, distinct from println) ────────────────
+
+function console_log(msg) {
+    // eslint-disable-next-line no-console
+    console.log(String(msg));
+}
+
 // ── Window export helpers ──────────────────────────────────────────────────
 //
 // Expose El functions to the browser's global scope so they can be called
@@ -783,6 +897,17 @@ const __el = {
     dom_set_prop, dom_get_prop, dom_set_style, dom_add_class, dom_remove_class,
     dom_show, dom_hide, dom_listen, dom_query, dom_query_all, dom_create,
     dom_append, dom_remove, dom_is_null,
+    // Extended DOM
+    dom_set_attr, dom_get_attr, dom_remove_attr, dom_set_html, dom_get_html,
+    dom_get_parent, dom_contains_class, dom_get_checked, dom_set_checked,
+    // Timers
+    set_timeout, set_interval, clear_interval,
+    // Local storage
+    local_storage_get, local_storage_set, local_storage_remove,
+    // Window location
+    window_location, window_redirect, window_on_load,
+    // Debug
+    console_log,
     // Window export helpers
     window_set, window_get,
     // native_js escape hatch
@@ -836,6 +961,17 @@ export {
     dom_set_prop, dom_get_prop, dom_set_style, dom_add_class, dom_remove_class,
     dom_show, dom_hide, dom_listen, dom_query, dom_query_all, dom_create,
     dom_append, dom_remove, dom_is_null,
+    // Extended DOM
+    dom_set_attr, dom_get_attr, dom_remove_attr, dom_set_html, dom_get_html,
+    dom_get_parent, dom_contains_class, dom_get_checked, dom_set_checked,
+    // Timers
+    set_timeout, set_interval, clear_interval,
+    // Local storage
+    local_storage_get, local_storage_set, local_storage_remove,
+    // Window location
+    window_location, window_redirect, window_on_load,
+    // Debug
+    console_log,
     // Window / native_js
     window_set, window_get, native_js, native_js_call,
 };

el-compiler/src/codegen-js.el

@@ -933,6 +933,12 @@ fn codegen_js(stmts: [Map<String, Any>], source: String) -> String {
     js_emit_line("  dom_set_prop, dom_get_prop, dom_set_style, dom_add_class, dom_remove_class,")
     js_emit_line("  dom_show, dom_hide, dom_listen, dom_query, dom_query_all, dom_create,")
     js_emit_line("  dom_append, dom_remove, dom_is_null,")
+    js_emit_line("  dom_set_attr, dom_get_attr, dom_remove_attr, dom_set_html, dom_get_html,")
+    js_emit_line("  dom_get_parent, dom_contains_class, dom_get_checked, dom_set_checked,")
+    js_emit_line("  set_timeout, set_interval, clear_interval,")
+    js_emit_line("  local_storage_get, local_storage_set, local_storage_remove,")
+    js_emit_line("  window_location, window_redirect, window_on_load,")
+    js_emit_line("  console_log,")
     js_emit_line("  window_set, window_get, native_js, native_js_call,")
     js_emit_line("} = globalThis.__el;")
     js_emit_blank()