Support hot reloading of environment variables and runtime code

Feature Request

Problem

When changing environment variables in settings.json (e.g., CLAUDE_CODE_NO_FLICKER=1), every running Claude Code instance must be manually restarted for the change to take effect. This is disruptive, especially when running multiple sessions.

Proposed Solution

Support hot reloading for:

1. Environment variables — Changes to env vars in settings.json should be picked up by running instances without a restart, similar to how keybindings and themes already reload dynamically.
2. Runtime code — Claude Code itself should support hot code swapping so that updates and config changes can be applied without restarting sessions and losing conversation context.

Current Behavior

• Keybindings and themes: reload dynamically
• Environment variables: require restart
• Code updates: require restart

Expected Behavior

All configuration changes and updates apply to running instances without requiring a restart.