docs(harnesses): restore Lili's original Anthropic Console link

Revert the Anthropic Console URL to platform.claude.com/login?returnTo=/?
per PR review feedback that the original link was correct.

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: hongyi-chen

src/content/docs/agent-platform/cloud-agents/harnesses/authentication.mdx

@@ -21,7 +21,7 @@ Claude Code is Anthropic's agentic coding tool. For more on Claude Code authenti
 
 ### Create an Anthropic API key
 
-1. Go to the [Anthropic Console](https://console.anthropic.com/) and sign in (or create an account).
+1. Go to the [Anthropic Console](https://platform.claude.com/login?returnTo=/?) and sign in (or create an account).
 2. Navigate to **API keys** and create a new key.
 3. Make sure your account has API credits — Claude Code runs are billed against your Anthropic API balance.