[BUG] CLI 'claude remote-control' fails at Registration with 401 despite valid Max login (Windows, v2.1.148)

Summary

claude remote-control fails immediately at the Registration phase — the first authenticated cloud-bridge POST, before any session is created — with a 401, even though the same OAuth login works fine for normal CLI use and the account is a valid Claude Max subscription. This is the well-known "RC 401 on valid Max" symptom from #30093 (closed), but at a different phase (registration, not poll) and on a different platform/version (Windows, v2.1.148).

Environment

• OS: Windows 11 Pro (10.0.26100)
• Claude Code: v2.1.148 (PATH = npm-global @anthropic-ai/claude-code)
• Also reproduced on v2.1.140
• Account: Claude Max (organizationType: claude_max, organizationRateLimitTier: default_claude_max_20x, billingType: stripe_subscription), org admin
• Shell: PowerShell 5.1
• No ANTHROPIC_API_KEY / custom apiKey set — OAuth is the only credential

Exact error

Error: Registration: Authentication failed (401): Invalid authentication credentials. Remote Control is only available with claude.ai subscriptions. Please use '/login' to sign in with your claude.ai account.

Steps to reproduce

1. /login with a claude.ai Max account; confirm normal CLI usage works.
2. Run claude remote-control --spawn session --name "test"
3. Approve workspace trust + "Enable Remote Control?" if prompted.
4. → fails at Registration with the 401 above. No session URL/QR is ever produced.

What I ruled out

• Account type — valid claude_max (admin, 20x tier, stripe subscription). claude auth status → loggedIn: true, type max. Token works for ordinary CLI calls in the same session.
• API-key shadowing — no ANTHROPIC_API_KEY or config apiKey overriding OAuth.
• Version — fails identically on v2.1.140 and v2.1.148.
• Workspace trust — already cleared; failure occurs past that gate.

Relationship to existing issues

• #30093 (closed) — same "RC 401 despite valid Max" symptom, but fails at the bridge poll phase on macOS v2.1.63. Ours fails earlier, at registration, on Windows v2.1.148.
• #59665 (open) — Windows RC failure too, but a different component: the desktop-app webview bridge (empty IndexedDB, 403 org-allowlist). Ours is the CLI registration POST, not the desktop webview.

Expected behavior

A valid claude.ai Max OAuth session should authenticate at the RC registration endpoint and produce a session URL/QR, rather than 401'ing with "Remote Control is only available with claude.ai subscriptions."