feat(analytics): add UTMs to docs signup links (GRO-86) (#924)

* feat(analytics): add UTMs to docs signup links (GRO-86)

So Growth can attribute new Arcade account creations back to docs —
per-page campaigns for the three QuickStarts, generic `docs` elsewhere.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor(analytics): prefix docs campaigns so startsWith("docs") catches all

- Default utm_campaign=docs (generic docs pages)
- QuickStarts use utm_campaign=docs-quickstart-<slug>
- Drop default utm_medium (most SignupLinks are inline prose, not CTAs)
- Navbar uses utm_medium=navbar (matches marketing site convention)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor(analytics): use URL constructor for SignupLink UTM assembly

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: teallarson

app/_components/analytics.tsx

@@ -8,12 +8,29 @@ export type LinkClickedProps = {
   linkLocation: string;
   children?: React.ReactNode;
   className?: string;
+  utmCampaign?: string;
+  utmMedium?: string;
+};
+
+const UTM_SOURCE = "docs";
+const DEFAULT_UTM_CAMPAIGN = "docs";
+
+const buildRegisterHref = (utmCampaign: string, utmMedium?: string): string => {
+  const url = new URL(getDashboardUrl("register"));
+  url.searchParams.set("utm_source", UTM_SOURCE);
+  url.searchParams.set("utm_campaign", utmCampaign);
+  if (utmMedium) {
+    url.searchParams.set("utm_medium", utmMedium);
+  }
+  return url.toString();
 };
 
 export const SignupLink = ({
   linkLocation,
   children,
   className,
+  utmCampaign = DEFAULT_UTM_CAMPAIGN,
+  utmMedium,
 }: LinkClickedProps) => {
   const trackSignupClick = (source: string) => {
     posthog.capture("Signup clicked", {
@@ -24,7 +41,7 @@ export const SignupLink = ({
   return (
     <Link
       className={cn("text-primary", className)}
-      href={getDashboardUrl("register")}
+      href={buildRegisterHref(utmCampaign, utmMedium)}
       onClick={() => trackSignupClick(linkLocation)}
     >
       {children}

app/en/get-started/quickstarts/call-tool-agent/page.mdx

@@ -20,7 +20,7 @@ Install and use the Arcade client to call Arcade Hosted Tools.
 
 <GuideOverview.Prerequisites>
 
-- An <SignupLink linkLocation="docs:call-tools-directly">Arcade account</SignupLink>
+- An <SignupLink linkLocation="docs:call-tools-directly" utmCampaign="docs-quickstart-call-tool-agent">Arcade account</SignupLink>
 - An [Arcade API key](/get-started/setup/api-keys)
 - The [`uv` package manager](https://docs.astral.sh/uv/getting-started/installation/) if you are using Python
 - The [`bun` runtime](https://bun.com/) if you are using TypeScript

app/en/get-started/quickstarts/call-tool-client/page.mdx

@@ -35,7 +35,7 @@ Create a coding agent using an MCP Gateway to call tools from multiple MCP serve
 
 <GuideOverview.Prerequisites>
 
-- An <SignupLink linkLocation="docs:call-tools-directly">Arcade account</SignupLink>
+- An <SignupLink linkLocation="docs:call-tools-directly" utmCampaign="docs-quickstart-call-tool-client">Arcade account</SignupLink>
 
 </GuideOverview.Prerequisites>
 

app/en/get-started/quickstarts/mcp-server-quickstart/page.mdx

@@ -158,7 +158,7 @@ $env:MY_SECRET_KEY="my-secret-value"
 
 ## Connect to Arcade to unlock authorized tool calling
 
-Since the Reddit tool accesses information only available to your Reddit account, you'll need to authorize it. For this, you'll need to create an Arcade account and connect from the terminal, run:
+Since the Reddit tool accesses information only available to your Reddit account, you'll need to authorize it. For this, you'll need to create an <SignupLink linkLocation="docs:mcp-server-quickstart" utmCampaign="docs-quickstart-mcp-server">Arcade account</SignupLink> and connect from the terminal, run:
 
 ```bash
 arcade login

app/layout.tsx

@@ -160,7 +160,7 @@ export default async function RootLayout({
               }
               projectLink="https://github.com/ArcadeAI/arcade-mcp"
             >
-              <SignupLink linkLocation="docs:navbar">
+              <SignupLink linkLocation="docs:navbar" utmMedium="navbar">
                 <NavBarButton
                   hideOnPath={[
                     "/guides/create-tools/add-tools-to-arcade-catalog",