feat(onboarding): propagate NEEDS_SIGNUP (code 4) through onboard-driver and muse-signin

bin/muse-signin.py

@@ -15,6 +15,13 @@ The operator then obtains the OTP (via chat with user) and re-runs:
 
 This keeps credentials out of the automation — the OTP is provided
 transiently via the operator, never stored.
+
+Exit codes:
+  0: Success / already logged in
+  2: APPROVAL_NEEDED (OTP prompt reached, awaiting code)
+  3: NEEDS_HUMAN (multi-account selection needs manual choice)
+  4: NEEDS_SIGNUP (account not found / registration required)
+  1: General error
 """
 import json, urllib.request, websocket, time, sys, argparse, importlib.util
 
@@ -199,6 +206,35 @@ def main():
             ws.close()
             sys.exit(1)
     else:
+        body_full = ev(ws, "document.body.innerText.slice(0,2000)") or ""
+        body_lower = body_full.lower()
+        signup_cues = [
+            "no account found",
+            "couldn't find your account",
+            "cannot find",
+            "create an account",
+            "create your account",
+            "create account",
+            "sign up",
+            "sign-up",
+            "doesn't have an account",
+            "not registered",
+            "register",
+            "get started"
+        ]
+        has_signup_cue = any(cue in body_lower for cue in signup_cues)
+        has_name_or_pwd = ev(ws, """(()=>{
+          const inps = [...document.querySelectorAll('input')];
+          return inps.some(i => (i.placeholder && i.placeholder.toLowerCase().includes('name')) ||
+                                (i.name && i.name.toLowerCase().includes('name')) ||
+                                (i.type === 'password'));
+        })()""")
+
+        if has_signup_cue or has_name_or_pwd:
+            print(f"NEEDS_SIGNUP: Account does not exist on Muse for {args.email}. Client must sign up first at https://muse.ai", file=sys.stderr)
+            ws.close()
+            sys.exit(4)
+
         print("No OTP prompt found - check page state", file=sys.stderr)
         print(f"Body: {body[:200]}", file=sys.stderr)
         ws.close()