feat(modal): add rollout telemetry foundation

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/js/core/modal-telemetry.js

@@ -0,0 +1,112 @@
+/**
+ * Frontend modal performance marks.
+ *
+ * Records only bounded domain/event names and timing data. Never include
+ * payment credentials, order contents, identity evidence, or user payloads.
+ *
+ * @package AKSRT
+ */
+(function (window) {
+  'use strict';
+
+  var allowedKinds = {
+    identity: true,
+    badges: true,
+    orders: true,
+    vip: true,
+  };
+  var allowedEvents = {
+    click: true,
+    shell: true,
+    'first-content': true,
+    ready: true,
+    'action-start': true,
+    'action-end': true,
+    unauthorized: true,
+    error: true,
+  };
+  var sessions = Object.create(null);
+  var sequence = 0;
+  var maxSessions = 100;
+
+  function normalize(value, fallback) {
+    var normalized = String(value || fallback || '').toLowerCase().replace(/[^a-z0-9-]/g, '');
+    return normalized || fallback;
+  }
+
+  function now() {
+    return window.performance && typeof window.performance.now === 'function'
+      ? window.performance.now()
+      : 0;
+  }
+
+  function markName(session, event) {
+    return 'aksrt-modal-' + session.kind + '-' + session.id + '-' + event;
+  }
+
+  function emit(session, event) {
+    if (!window.performance || typeof window.performance.mark !== 'function') return;
+
+    var name = markName(session, event);
+    window.performance.mark(name);
+    session.marks[event] = name;
+
+    if (typeof window.performance.measure === 'function' && session.marks.click && event !== 'click') {
+      try {
+        window.performance.measure(
+          'aksrt-modal-' + session.kind + '-' + session.id + '-click-to-' + event,
+          session.marks.click,
+          name
+        );
+      } catch (error) {
+        // A missing mark must never affect the modal interaction.
+      }
+    }
+  }
+
+  function start(kind) {
+    var safeKind = normalize(kind, 'unknown');
+    if (!allowedKinds[safeKind]) safeKind = 'unknown';
+
+    sequence += 1;
+    var id = String(sequence);
+    var session = {
+      id: id,
+      kind: safeKind,
+      startedAt: now(),
+      marks: Object.create(null),
+    };
+
+    sessions[id] = session;
+    emit(session, 'click');
+
+    var ids = Object.keys(sessions);
+    while (ids.length > maxSessions) {
+      delete sessions[ids.shift()];
+    }
+
+    return id;
+  }
+
+  function mark(id, event) {
+    var session = sessions[String(id || '')];
+    var safeEvent = normalize(event, 'error');
+    if (!session || !allowedEvents[safeEvent]) return;
+    emit(session, safeEvent);
+  }
+
+  function finish(id) {
+    mark(id, 'ready');
+  }
+
+  function fail(id) {
+    mark(id, 'error');
+  }
+
+  window.AksrtModalTelemetry = {
+    start: start,
+    mark: mark,
+    finish: finish,
+    error: fail,
+  };
+})(window);