fix(analytics): stop orphaning anonymous person on load, breaking signup attribution

__root identify effect called posthog.reset() whenever `user` was falsy —
which includes the brief window while the session resolves on every page
load. After the signup hard-redirect this rotated the anonymous distinct_id,
orphaning the pre-signup anonymous person that carries `user_signed_up` and
first-touch `$initial_utm_*`. The later identify() then merged a fresh, empty
anon id, so signups never linked to trial/payment (only ~16% stitched) and
channel attribution read "(none)" for 100% of signups.

- __root.tsx: gate the effect on isLoading and only reset() on a real
  identified -> anonymous transition (logout), tracked via a ref. Logout
  still resets via dashboard handleSignOut.
- register.tsx: identify() within the still-active anonymous session before
  firing user_signed_up, so the anon->identified merge carries $initial_utm_*
  and attributes the signup (email flow; Google is handled on OAuth return).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/web/src/routes/__root.tsx

@@ -11,7 +11,7 @@ import { Button } from "@sase/ui";
 import type { QueryClient } from "@tanstack/react-query";
 import { Link, Outlet, createRootRouteWithContext, useLocation } from "@tanstack/react-router";
 import { ArrowLeft, Home, Search } from "lucide-react";
-import { useEffect } from "react";
+import { useEffect, useRef } from "react";
 
 interface RouterContext {
   queryClient: QueryClient;
@@ -93,7 +93,7 @@ function applyTheme(theme: "light" | "dark" | "system") {
 
 function RootComponent() {
   const location = useLocation();
-  const { user } = useAuth();
+  const { user, isLoading } = useAuth();
   const { t } = useTranslation();
 
   // Pageview tracking
@@ -102,9 +102,22 @@ function RootComponent() {
     trackMetaPageView();
   }, [location.pathname]);
 
-  // User identification
+  // User identification.
+  //
+  // CRITICAL: never call posthog.reset() while the session is still resolving,
+  // nor for first-time anonymous visitors. reset() rotates the anonymous
+  // distinct_id; firing it on every load (user is briefly null while the
+  // session loads) orphaned the pre-signup anonymous person — the one that
+  // carries `user_signed_up` and the first-touch `$initial_utm_*`. The later
+  // identify() then merged a fresh, empty anon id instead, so signups never
+  // linked to trial/payment and channel attribution read "(none)" for everyone.
+  // Only reset on a genuine identified -> anonymous transition (logout);
+  // explicit logout also resets via dashboard.tsx's handleSignOut.
+  const wasIdentifiedRef = useRef(false);
   useEffect(() => {
+    if (isLoading) return; // session still resolving — leave identity untouched
     if (user) {
+      wasIdentifiedRef.current = true;
       identifyUser({
         id: user.id,
         email: user.email,
@@ -117,11 +130,12 @@ function RootComponent() {
         .get<{ identifier: string; identifierHash: string }>("/chatwoot/identity")
         .then((res) => setChatwootUser(user, res.identifierHash))
         .catch(() => {});
-    } else {
+    } else if (wasIdentifiedRef.current) {
+      wasIdentifiedRef.current = false;
       resetUser();
       resetChatwootUser();
     }
-  }, [user]);
+  }, [user, isLoading]);
 
   useEffect(() => {
     const theme = getUserSettings().theme ?? "dark";

apps/web/src/routes/_auth/register.tsx

@@ -3,7 +3,7 @@ import { api } from "@/lib/api-client";
 import { signIn, signUp } from "@/lib/auth-client";
 import { startAction } from "@/lib/faro";
 import { track as trackMeta } from "@/lib/meta-pixel";
-import { capture } from "@/lib/posthog";
+import { capture, identifyUser } from "@/lib/posthog";
 import { toast } from "@/lib/toast";
 import { cleanModelName } from "@/lib/vehicle";
 import { Button } from "@sase/ui";
@@ -96,7 +96,7 @@ function RegisterPage() {
       // better-auth returns { error } rather than throwing (see login.tsx).
       // The old code awaited without checking error, so failed signups still
       // reported success, fired user_signed_up, and redirected to the dashboard.
-      const { error } = await signUp.email({
+      const { data, error } = await signUp.email({
         name,
         email,
         password,
@@ -129,6 +129,21 @@ function RegisterPage() {
         return;
       }
 
+      // Identify within the still-active anonymous session, BEFORE the signup
+      // event and the hard redirect below. This merges the anonymous person
+      // (which holds first-touch `$initial_utm_*`) into the user and attributes
+      // `user_signed_up` to them — so channel → signup → trial/paid is linkable.
+      // (Google OAuth redirects away here, so it's identified on return by
+      // __root's effect instead.)
+      if (data?.user) {
+        identifyUser({
+          id: data.user.id,
+          email: data.user.email,
+          name: data.user.name,
+          role: (data.user as { role?: string }).role ?? "user",
+        });
+      }
+
       // The referral code travels via `?ref=` in redirectUrl; the welcome
       // onboarding modal on the search page is the single place that applies it
       // (covers both email and Google OAuth signups).