feat(studio): drag items in the preview, snapping to the canvas, items, spacing, and a grid

README.md

@@ -75,7 +75,7 @@ Every panel is a tab you can drag, split, or stack.
 
 | Panel | Use it to |
 | --- | --- |
-| Preview, Program | See the scene you are editing and the one that is live. **Cut** puts the preview on program at once; **Fade** blends over the collection's fade time. |
+| Preview, Program | See the scene you are editing and the one that is live, and drag items in the preview to place them. **Cut** puts the preview on program at once; **Fade** blends over the collection's fade time. |
 | Scenes | Pick the scene in preview, add one, or remove one. |
 | History | See every edit, and undo or redo back to any of them. |
 | Items | Place, show, hide, and order what the preview scene or the top layer draws, back to front. Select an item to filter or copy it. |
@@ -91,6 +91,14 @@ Items panel shows. The **top layer** is drawn over every scene, in preview and
 on program, and stays on through a cut or fade: a downstream keyer for a logo
 or a lower third.
 
+In the preview, click an item of whatever the Items panel shows to select it,
+drag it to move it, and drag its edges or corners to resize it. A drag snaps
+edges and centers to the canvas's edges and center, to the other items shown,
+and to the grid while **Grid** is on, drawing a guide through what it lines up
+with. A moved item also snaps to the spacing of its neighbors, marking the
+equal spaces. Hold Ctrl (Cmd on macOS) to drag without snapping, or turn
+**Snap** off. The snap and grid settings last until the studio quits.
+
 Items showing the same source are **linked**: one capture, with the source's
 filters, wherever it is shown. A **clone** is a new source showing another's
 capture with filters of its own, so a camera can be shown faded in one scene

quest/m0/README.md

@@ -95,7 +95,6 @@ repository.
 - [HTML/CSS overlays](/quest/m0/overlays.md) - script-free HTML and CSS graphics through Blitz natively and the DOM in the browser
 - [Animation and transitions](/quest/m0/animation.md) - move, slide, wipe, and stinger transitions, and keyframed item properties
 - [Video effects](/quest/m0/effects.md) - a curated effect set with CSS meanings, and ML effects baked into their source
-- [Snapping and guides](/quest/m0/snapping.md) - preview moves snap to edges, centers, and other items
 - [Destinations](/quest/m0/destinations.md) - RTMP, RTMPS, and WHIP push with per-destination codecs and shared encoders, on a UI-free egress library a hosted service can reuse
 - [Multiple canvases](/quest/m0/multi-canvas.md) - landscape and portrait canvases composite at once from shared sources
 - [Guests](/quest/m0/guests.md) - remote guests and phone cameras join through a moq-room link or QR code and appear as sources

rs/moq-studio/src/main.rs

@@ -14,6 +14,7 @@ mod devices;
 mod engine;
 mod health;
 mod setup;
+mod snap;
 mod ui;
 mod uplink;