Structured startup-refusal reasons for host integrations

Claude Code can now report a specific, structured reason when it refuses to start, instead of just failing silently or with a generic message. This is meant for a host application (like an IDE extension or desktop wrapper) that embeds Claude Code, so it can react to the specific cause rather than just retrying blindly. New reason values include:

• worktree_resume_refused and worktree_unverified (problems resuming a git worktree, an isolated working copy of a repo)
• session_held_by_background (another process is using the session)
• bypass_root (a root-related safety check)
• shell_tool_missing, tied to the CLAUDE_CODE_USE_POWERSHELL_TOOL setting
• cli_version_too_old
• gateway_signin_required and gateway_access_denied
• org_pin_api_key_conflict, org_verify_failed, org_pin_mismatch
• managed_settings_invalid and remote_settings_required_unavailable
• proxy_invalid
• temp_dir_unusable and cwd_unavailable