Publish harness and TUI open-source

initial sync from the monorepo

crates/codegen/xai-grok-shell/changelogs/0.2.18.md

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+# 0.2.18
+
+## Features
+
+- **Official xAI plugin marketplace** now appears automatically in the Marketplace tab on first launch.
+- **Image and video generation** now use api.x.ai directly for all users.
+- **New image-to-video and reference-to-video tools** are now available for generating videos from images.
+- **New imagine skill** provides prompt-craft and workflow guidance for image generation and editing tools.
+
+## Bug Fixes
+
+- **image_edit** now correctly resolves pasted or attached images referenced as [Image #N].
+- **Background subagent completions** are no longer reported twice when the agent is idle.
+- **Subagents** now use the same model as the parent session by default.
+