A sketch should not look like plate preparation

Three cues, because one is missed. A teal banner across the top of the viewport names the session
("Editing: Sketch N") and where its exits are; the printer bed is muted for the duration, since a
plate grid and a sketch grid are the same visual language and reading one as the other is how a
sketch gets drawn against the wrong reference; and N looks straight down the plane normal at the
current zoom, with the plane's own y axis as up, because no hand-orbit lands exactly square and a
sketch read at an angle is one whose right angles do not look like right angles.

The banner is an INDICATOR. Finish and Cancel stay on the single ribbon action bar — the tab had
three competing confirm surfaces once and that is not being reopened for a strip of colour. It
sits above the canvas rather than floating inside it: a child window over a wxGLCanvas is a native
window on GTK with no reliable stacking over GL, and being unmissable beats being clever.

The bed checkbox stays the stored preference and is restored on leaving the sketch; ticking it
mid-sketch still shows the bed, because that is a deliberate act and this is only a default.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011FbJKJAJxxkhDTs9XdZzKA

docs/CAD/ux/interaction-model.md

@@ -109,3 +109,36 @@ also mean "open a menu".
 
 Right-hold-and-drag is not in the table on purpose: past 3 px or 200 ms it is navigation, and
 navigation does not transition the state machine.
+
+## 4. Visual scaffolding
+
+Entering a sketch changes three things at once, so the state is legible from across the room:
+
+- **Banner.** A teal strip across the top of the viewport: `Editing: Sketch N · N = look normal to
+  the plane · Finish or Cancel in the toolbar`. Indicator only — Confirm and Cancel stay on the one
+  ribbon action bar, per the Design UX contract. It is a sibling above the canvas, not a floating
+  child over it: a child window over a `wxGLCanvas` is a native window on GTK and does not reliably
+  stack over GL, and this banner's job is to be unmissable rather than clever.
+- **The printer bed is muted.** A plate grid and a sketch grid are the same visual language, and
+  reading one as the other is how a sketch gets drawn against the wrong reference. The view
+  checkbox remains the stored preference and is restored on the way out; ticking it mid-sketch
+  still shows the bed, because that is a deliberate act and this is only a default.
+- **`N` looks normal to the plane**, keeping the current zoom, with the plane's own y axis as up.
+  Sketch key map only — in Feature mode the navigator orb owns orientation.
+
+## 5. Context menu content
+
+The offer is generated from `docs/CAD/ux/tool_atlas.json`; its 8-row shape and permanent row
+indices are ratified and are not changed here. Checked against the per-context vocabularies asked
+for in the 2026-09-05 interaction brief, the atlas already carries all of them except two, both on
+a planar face:
+
+| Asked for | Status |
+|---|---|
+| Revolve on a planar face | **not offered, and should not be**: `revolve` accepts `sk_loop` only, because the kernel takes a sketch profile — a face is not one |
+| Offset Face | offered as **Thicken** (`thicken`, accepts `face_planar`); `surf_offset` is the sheet-body verb and accepts `body_sheet` |
+
+View and document actions — Zoom to Fit, View Isometric, Clear Selection, Finish Sketch, Normal to
+Sketch — stay in chrome by the atlas's own rule: the offer describes verbs that consume a
+*selection*, and these act on the document or the camera. Esc covers Clear Selection, `N` covers
+Normal to Sketch, and the ribbon covers Finish.