Grok Build adds jump, timeline sidebar

Grok Build is addressing usability friction in long coding conversations by adding quick navigation commands and environmental consistency, positioning itself more aggressively against existing CLI coding agents.

* The `/jump` command is a crucial developer experience quality-of-life feature that prevents losing progress when reverting to earlier prompts.

* The `/timeline` sidebar addresses the UI challenge of managing long-context developer sessions in terminal or web views.

* Preserving shell environment variables across local sessions ensures a more seamless terminal-native integration for developers who rely on complex configurations.