Website builder fixes: elements palette, autosave, panel layout and canvas handles

A round of fixes to the redesigned website builder. Classes now do what classes are for: style an element that has a class and every element sharing it updates too - previously the change stayed on the one element. The style selector also spells out what you're editing ("Editing .button - affects every element with this class"), and you can click a class to include or exclude it from the rule, so styling .button and .button.is-large are both one click away. Saved components keep their styling: they used to save the markup only, so dropping one on another page gave you an unstyled copy. Saving a component now happens in a proper dialog with a dropdown of your existing groups instead of two browser prompts, and those groups finally show up as headings in the Add panel. Copies stay linked to the original - edit the component once and every instance updates - and they're labelled "Component (linked)" so that's obvious; right-click and Detach if you want one to differ. Dropped sections are no longer black boxes: the Navigator now shows each one as a labelled outline - Hero → Container → Heading, Text, Row → Button - so you can click straight to the piece you want, restyle it, or pull it into a layout of your own. Building from scratch got easier too, with plain Section, Container and Div elements plus vertical, horizontal and grid boxes. The column rows were rebuilt as well - 2, 3 and 4 columns and two sidebar splits - and they're now proper grids, so with a row selected you add or remove a column from the Layout panel in one click, and set it to a single column on mobile without touching the desktop layout. The old column blocks styled every row on the site at once and stacked at a screen size the builder didn't even offer. Grid layouts no longer need you to know CSS: pick Grid and just type how many columns and rows you want. Previously the field wanted CSS track syntax, and typing a plain "3" was invalid CSS the browser threw away - so nothing happened. Aspect ratio is a named list - Square, Widescreen, Portrait and so on - and image cropping is a nine-point grid rather than a pair of percentages. Interactions now play when you hit ▶ Preview in the builder: previously animations stayed frozen there, which was the one place you'd go to check them. Scroll-triggered animations also fire correctly on sections taller than the screen, which used to stay invisible. The Elements and Layouts palette no longer sits on "Loading…" - it fills in as soon as the editor opens. Autosave now actually persists: page edits were being saved correctly but discarded when the page was read back, so reopening a page showed the old version; that's fixed, and if a save ever does fail you'll see it in the top bar instead of it failing quietly. Saving page settings no longer reloads the canvas and loses unsaved work. The old leftover toolbar that overlapped the top bar and the Style tab is gone, which also removes the buttons that could quietly put the editor into a state where clicking an element stopped opening its panel - and selecting an element now always reveals the panel. Paired controls like Width/Height and Min/Max no longer overlap in narrow panels: their labels sit above the field, wide option pickers wrap instead of squashing, and the panels can be dragged wider. Every numeric field is now click-and-type as well as drag-to-scrub - including the spacing box, where a single click opens a text field - and slider readouts (opacity, blur, shadow offsets) are editable, so you can enter an exact value anywhere. Finally, the canvas resize handles stay locked to the edges of the page frame when you switch breakpoints, and can no longer be dragged off-screen or over the side panels.