# M4: app shell

Branch: `m4-app-shell` → `main`

## What changed

- **Wails v3.1.0 app** (latest stable; the plan said 3.0.0). It needs Go 1.26, so `go.mod` now says `go 1.26.0`.
  - `main.go`: one 1280×860 window (minimum 760×600) with the mockup's background colour, the `app.Service`, and the embedded `frontend/dist`.
  - `Taskfile.yml` and `build/` come from `wails3 init -t svelte`, without the Android, iOS and Docker parts. `build/config.yml` names the product mpckit, (c) 2026 bajdev, "Not affiliated with Akai Professional"; the Windows version info was regenerated from it. Icons are still the Wails defaults (M9).
- **`internal/app`**: the Wails service (build plan 4.6, 5). For M4: `New()`, `State()`, `Version()`, `About()`. `State` holds the project name, the dirty flag, all 128 pads (label `A01`…`H16`, sample, tuning, mute group, has-notes), the sequences, counts, and the device limits (mute groups 0–16, BPM 20–999, tuning ±24/±90) so the UI never hard-codes them. `Version` is set with `-ldflags` (M9) and is `dev` until then.
- **Frontend** (Svelte 5 + TypeScript + Vite), following the mockup:
  - Title row with About; project name; New / Load / Export zip / Export to folder; Pads and Sequences tabs.
  - Each tab has bank buttons A–H with per-bank counts, the 4×4 grid (pad 1 bottom-left), a settings panel for the selected slot, and a footer with counts.
  - `lib/store.svelte.ts` holds the Go state (replaced after each call) and UI-only state (tab, bank, selection, About).
  - Components: `BankBar`, `SlotGrid` (shared by both tabs), `PadPanel`, `SequencePanel`, `AboutModal`.
  - The About modal shows version, licence, the repo link (opens in the system browser) and the no-affiliation note. It closes with Escape, the Close button or a click outside.
  - Fonts (Inter, Space Grotesk, IBM Plex Mono, all OFL) come from `@fontsource` packages, so the app needs no network.
- **Bindings** in `frontend/bindings`, generated by `wails3 generate bindings -ts -i` (regenerated on every build).
- `frontend/dist/.gitkeep` is committed so `go build` / `go test ./...` work in a fresh clone (main.go embeds dist). A small Vite plugin puts it back after each build.
- **README**: development setup (Go 1.26, Node LTS, `wails3`, `wails3 dev`). The build plan's Wails version and setup lines are updated.

## What works in M4 and what doesn't yet

Working: data comes from Go (`State()` on start, `New()` from the New button); tabs (click or arrow keys); bank switching; selecting pads and sequence slots; the settings panels showing the selected slot's values; About.

Shown but **disabled** until their milestone, with a note in each panel: Load, Export (M5/M8), the name field, all pad controls (M5/M6), all sequence controls (M7).

## Testing

On the server:
- `go vet` and `go test` pass for all Go packages. `internal/app` has tests for the new-project state, its JSON shape and About.
- The main package vets and builds for Windows (`GOOS=windows`, an 18 MB `mpckit.exe`), and vets for Linux and macOS with `-tags purego`.

**Not tested on the server:** it has no Node.js, so the frontend has not been built, type-checked (`svelte-check`) or seen running. Please check on the laptop:

1. `wails3 doctor` is happy; `wails3 dev` builds and opens a window titled mpckit (the first run does `npm install`).
2. The page matches the mockup's layout and colours. Project name "NewKit"; footer "0 of 128 samples", "1 of 128 sequences".
3. Pads tab: bank A selected, 16 empty pads with A01 at bottom-left and A16 at top-right; clicking a pad moves the orange outline and the settings panel shows "This pad is empty". Bank buttons switch banks.
4. Sequences tab: A01 shows "Sequence 01", "128 · 2 bars". Selecting it shows name, BPM 128, 2 bars. Empty slots show "No sequence in this slot".
5. About opens and closes (Escape, Close, click outside); the repo link opens your browser.
6. New resets the state (no visible change on a new project, but there should be no error).
7. `npm run check` in `frontend` (svelte-check) reports no errors.

Please send screenshots or errors. Anything wrong in the Svelte side I'll fix on this branch.