Consolidate remaining package main files into internal/termapp for
clean separation: cmd/serialterminal/ is the sole entry point.
Update .goreleaser.yaml to build from ./cmd/serialterminal.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Extract ConvertChunk/FormatHexFrame into pkg/charset (zero external deps).
Extract UIEvent/UIEventKind/UIPanelKind types into internal/event.
Update all references across main package to use qualified imports.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
JiXieShi