Background jobs check and keep ANTHROPIC_PROFILE and ANTHROPIC_CONFIG_DIR

A background job saves the environment it runs with, its environment variables, to a state file. Before, only CLAUDE_CODE_ATTRIBUTION_PROJECT and path variables were checked there. Now Claude Code also:

• Checks that ANTHROPIC_PROFILE is a valid profile name, the Anthropic profile to sign in with.
• Checks that a saved sign-in record is valid.
• Keeps ANTHROPIC_CONFIG_DIR, tidied into a standard path form.

The code that reads saved sign-in tokens also now returns nothing under a new condition.