Merge wp/B1

# Conflicts:
#	crates/engine/src/cmd/swatch.rs
#	crates/ui-egui/src/dialogs/mod.rs
#	crates/ui-egui/src/panels/mod.rs
#	docs/control-protocol.md

docs/control-protocol.md

@@ -19,6 +19,7 @@
 | `ui.render` | `{path?, scale?}` | render the artboard headlessly (PNG) |
 | `ui.resize` / `ui.focus` | | |
 | `app.open` / `app.save` / `app.export` / `app.quit` | `{path}` / `{path?}` / `{path?, format?, artboard?, range?, scale?, …}` | `app.open` reads every format `document.open` reads (see `document.formats`). `app.export` encodes through the engine's `document.export` (same options; the document keeps its path) and writes `path` through the host; without `path` it returns `{dataBase64, format, bytes}`, as headless mode does. `app.quit`, `file.close` and `file.closeAll` first open a `saveChanges` dialog for each modified document (they return `{"pending": "saveChanges"}`): `ui.dialog.confirm` saves, `ui.dialog.set {field: "discard", value: true}` then confirm discards, `ui.dialog.cancel` cancels the whole close or quit |
+| `ui.dialog.*` on `gradientStop` | `{field: "color" \| "opacity" \| "location", value}` | double-clicking a stop on the Gradient tool's annotator opens its popover (fields `index`, `x`, `y`, `tab`); set `color` (hex), `opacity` or `location` (percentages) and `ui.dialog.confirm` to apply them to the selected stop. `gradient.selectStop {index}` picks the stop the annotator, the panels and Delete/←/→ (`ui.key`) act on |
 
 Swatch editors: `engine.execute` with `ui.swatchOptions {name}` opens the `swatchOptions` dialog for a colour swatch
 (fields `name`, `spot`, `global`, `mode`: `gray`/`rgb`/`hsb`/`cmyk`/`web`, `color`: `"#rrggbb"` or a colour object,