[Feature Request] Support multiple OAuth accounts in a single installation

Problem

Currently, Claude Code supports only one active OAuth account at a time. To switch accounts, users must /logout and re-authenticate each time. This is inconvenient for users who regularly work across multiple accounts (e.g., personal + team, or multiple organizations).

Proposed Solution

Allow registering multiple OAuth accounts and switching between them without re-authentication.

For example:

/account list          # show registered accounts
/account switch <name> # switch active account

Use Case

• Developers working across personal and team/enterprise accounts
• Contributors to multiple organizations with separate billing
• Testing with different account tiers (Pro, Max, Enterprise)