docs: ribbon redesign proposal (#1439)

* docs: ribbon UX redesign proposal (mockups and notes)

Seven mockup images and a short description of the proposed ribbon shell, with floating and
compact layout options. Pictures only; no app changes. The sketch variant with tab locks is
left out.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

* docs: update the UX mockups to the current command set

Adds the Sketch Pattern panel, Perforate, new joints and motion commands, Fair and Match Surface,
and the Render workspace; the workspace switcher now matches the app (Design and Render available,
Animation, Simulation, Manufacture and Drawing later). Command map covers all 389 commands.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

* docs: draw the UX mockups with the reviewed icon SVGs and accents

Ribbon, browser, history and navigation icons now come from the icon system in #853, with the
Sketch tab in the Sketch green and constraints in red.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

* docs: address review on the UX proposal README

Describe the current toolbar in our own terms, and list only Design and Render as the workspaces in
scope.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/design/ux-redesign/README.md

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+# UX redesign proposal: ribbon layout
+
+Design mockups for a new desktop shell. They are pictures only: nothing in the app changes with
+this proposal. The goal is a layout that is familiar to people coming from other CAD software and
+easy for new users, built from standard patterns, with the current single-row toolbar replaced by
+a ribbon whose tabs are ordered by task instead of by geometry type.
+
+![Model tab, floating](model-floating.png)
+
+## The design
+
+**Application bar** (dark): logo and name, a house icon that opens the start page, Save, Undo,
+Redo, the design tabs (each with a close button), then the agent status, Settings, Help and
+Report a bug. There is no search box here, no dark-mode toggle and no status bar.
+
+**Ribbon**: a workspace card at the left (Design and Render), tabs **Model, Surface, Assemble, Insert, Inspect, Manage, View**, and a small command
+search at the right end of the tab row (also the S key). Each section shows one to four promoted
+commands. Its label (▾) opens a list of every command in the section, and hovering a row pins it
+to the ribbon, as in the current app. Tooltips show the shortcut and modifier keys.
+
+**Contextual tabs** appear when the design needs them and are selected automatically:
+**Sketch** while a sketch is open (Create, Modify, Pattern, Constrain, Reference), **Sheet Metal** when the active body has a sheet-metal rule.
+Nothing is greyed out, and the other tabs stay available. Plastic features live in
+Model › Create ▾ and plastic rules in Manage, so there is no Plastic tab.
+
+**Viewport and panels**: the viewport is full-bleed under the application bar. The view compass is
+fixed at the top right and panels open below it. History is a full-width icon strip along the
+bottom edge.
+
+**Start page**: the house icon opens a full-page view with New, Open, Recent, Samples and crash
+recovery; Save As and Export are there too. The camera's Home view stays in the navigation bar.
+
+**Workspaces** are product modes that share the same design, history and selection and change only
+the ribbon tabs. The geometry types (Solid, Surface, Mesh) are tabs, not workspaces. Only Design
+and Render exist today and are the scope of this work; the switcher mockup also greys out the
+entries the app's own workspace menu already lists as "coming later".
+
+| Board | What it shows |
+|---|---|
+| [Command map](command-map.png) | All 389 commands regrouped by task, and where today's panels go |
+| [Floating](model-floating.png) | Model tab with the ribbon, browser and dialog floating over the viewport, Modify list open |
+| [Compact](model-compact.png) | The same tab docked to the window edges (see below) |
+| [Sketch](sketch.png) | Sketch tab with Finish Sketch as its own ribbon group |
+| [Sheet metal](sheet-metal.png) | The contextual tab opened on a sheet-metal body |
+| [Start page](start-page.png) | The house icon's full-page view |
+| [Workspaces](workspaces.png) | The workspace switcher, open |
+
+## Options
+
+**Floating** (above) keeps the ribbon, browser and dialogs as rounded cards over a full-bleed
+viewport. It looks lighter and keeps the 3D view visible around every panel.
+
+**Compact** docks the ribbon and the workspace card into one bar at the top with no gap, docks the
+browser flush to the left edge and ribbon (concave corner where they meet, only as tall as its
+contents), and docks a denser feature panel to the right edge below the compass. Spacing is a
+little tighter throughout. It maximises viewport space and still looks finished.
+
+![Model tab, compact](model-compact.png)
+
+Both options use the same dense feature panel: 24 px rows, a narrow label column, two-column
+options and collapsed sections, so commands with 10 to 20 options fit.
+
+## Not included
+
+- The earlier sketch variant with tab locks and a Finish menu was set aside as too complex for a
+  first version, and is not part of this proposal.
+- The icons in the mockups are the reviewed SVGs from the icon system in PR #853
+  (`assets/icons/ui/design/svg/`), coloured with its accents from `palette.toml`: Sketch tools in
+  the Sketch green, constraints in red, everything else in the Solid blue. The greyed Simulation and
+  Manufacture entries in the switcher mockup use placeholder icons and are not part of this work. This proposal does not
+  implement or change any app icons.