The copiedMsg state was referenced in the Copy MD button but never declared,
causing a ReferenceError crash at runtime. Also removed unused compress
logic (collapseHistory/forceExpand), dead functions (renderContent, formatText,
CodeBlockWithCopy, MermaidBlock), and unused imports (useMemo, mermaid).
🤗 Generated with Crush
Assisted-by: GLM-5.1 via Crush <crush@charm.land>