Fix cookie tracking for docs (#35937)

`npx convex docs` uses a link with the query param `t` but docs looks for `c`.

GitOrigin-RevId: c396b10dc192dc0cfd0eb818201b2c5c8ea46529

Author: sshader

npm-packages/docs/src/plugins/pagelogger.js

@@ -8,7 +8,7 @@ export default (function () {
 
   const currUrl = new URL(location);
   const params = currUrl.searchParams;
-  const cookieValue = params.get("c");
+  const cookieValue = params.get("t");
   if (cookieValue) {
     const isDev = currUrl.hostname.includes("localhost");
     const domain = isDev ? currUrl.hostname : "convex.dev";