extra — residual extra utilities

extra is a repository for extra utilities that are not part of the core residual toolset. These are auxiliary, often office-style, single-purpose tools that follow the same conventions as the rest of residual:

• amber-on-black aesthetic (via core/lib/tui/theme, transparent backgrounds by default)
• standalone res-* binaries (no runtime dependency on other res-* binaries)
• shared logic lives in core/lib/ and extra/lib/<util>/
• each top-level directory is an independent Go module / git repo

Utilities

Binary	Purpose
res-calc	Interactive amber calculator
res-sheets	Amber TUI spreadsheet (formulas, ranges, save/load)
res-code	IDE editor (tabs, sidebar, terminal)

Shared logic for every utility lives under extra/lib/<util>/; each binary is a thin entry point under extra/cmd/res-<util>/. This mirrors the core/lib convention.

Layout

extra/
├── lib/
│   ├── calc/          shared logic for the calculator utility
│   └── sheets/        spreadsheet model (ref, cell, dims)
│       ├── store/     Plan A persistence (zip + sqlite)
│       └── tui/       bubbletea grid UI
├── cmd/
│   ├── res-calc/      res-calc binary entry point
│   └── res-sheets/    res-sheets binary entry point
└── go.mod             module git.merith.xyz/residual/extra

Build & test

go build ./...
go test ./...