Feature request: per-project account pinning

Problem

When using Claude Code across multiple projects — some on a personal account, others on a team/org account — there's no way to pin which account a project should use. The /login command is global, so switching projects risks accidentally burning usage on the wrong account.

Proposed solution

Allow a per-project setting (e.g., in .claude/settings.local.json) to declare which account a project expects:

{
  "account": "user@example.com"
}

Behavior:

• On session start, if the active account doesn't match, show a warning or prompt to /login
• Optionally, block execution entirely with an error until the correct account is active
• The setting should be in settings.local.json (gitignored) since account identity is user-specific, not shared

Use case

I work on personal projects (personal account) and company projects (team account). Without account pinning, I have to manually verify via /usage before each session to avoid charging the wrong account. A declarative per-project setting would eliminate this risk.

Alternatives considered

• Separate terminal profiles per account — works but fragile and easy to forget
• Always checking /usage before starting — manual and error-prone