Add persistent sketch-constraint system (ocs_gcs port) and named-parameters handoff docs

Ports FreeCAD's planegcs 2D geometric constraint solver to Rust as a new
crates/ocs_gcs workspace member, and wires it into the document/scene model
as a persistent SketchConstraintSet: Coincident, Horizontal/Vertical,
Parallel/Perpendicular, Equal, Tangent, Distance, Angle and Radius
constraints that re-solve live (including mid-drag, not just on release),
render glyphs and a DOF badge, flag conflicts with a one-click resolver
pill, and round-trip through save/load via an XRecord blob.

Also includes docs/command_reference.md (a statically generated reference
of every registered command and its prompt sequence) and
docs/named_parameters_design.md + docs/backlog.md, which hand off the next
queued feature (a named-parameter/expression table) and consolidate every
deliberate scope-down and open gap found along the way, so a fresh session
has a complete starting point.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/ui/window/options.rs

@@ -41,6 +41,8 @@ pub fn view_window<'a>(
     crosshair_color: Option<[u8; 3]>,
     crosshair_color_input: &'a str,
     lineweight_display_scale: i32,
+    ribbon_label_font_size: i32,
+    ribbon_group_title_font_size: i32,
     model_space: &'a crate::app::config::ModelSpaceThemeConfig,
     model_bg_input: &'a str,
     paper_bg_input: &'a str,
@@ -535,6 +537,56 @@ pub fn view_window<'a>(
             text(crate::t!("Changes the on-screen width in Model without affecting plotted output."))
                 .size(11)
                 .width(sizing.width),
+        )
+        .push(Space::new().height(24))
+        .push(text(crate::t!("Ribbon")).size(15))
+        .push(Space::new().height(10))
+        .push(
+            row![
+                text(crate::t!("Icon label size")).size(12).width(140),
+                slider(
+                    8..=16,
+                    ribbon_label_font_size.clamp(8, 16),
+                    Message::RibbonLabelFontSizeChanged,
+                )
+                .step(1)
+                .width(Fill),
+                text(format!("{}px", ribbon_label_font_size.clamp(8, 16)))
+                    .size(11)
+                    .width(44),
+            ]
+            .spacing(10)
+            .align_y(iced::Center),
+        )
+        .push(Space::new().height(6))
+        .push(
+            text(crate::t!("Font size of the caption under each ribbon button's icon."))
+                .size(11)
+                .width(sizing.width),
+        )
+        .push(Space::new().height(10))
+        .push(
+            row![
+                text(crate::t!("Section title size")).size(12).width(140),
+                slider(
+                    7..=14,
+                    ribbon_group_title_font_size.clamp(7, 14),
+                    Message::RibbonGroupTitleFontSizeChanged,
+                )
+                .step(1)
+                .width(Fill),
+                text(format!("{}px", ribbon_group_title_font_size.clamp(7, 14)))
+                    .size(11)
+                    .width(44),
+            ]
+            .spacing(10)
+            .align_y(iced::Center),
+        )
+        .push(Space::new().height(6))
+        .push(
+            text(crate::t!("Font size of each panel's own title (Draw, Modify, Layers, …)."))
+                .size(11)
+                .width(sizing.width),
         );
 
     let display_element = display.spacing(0).width(sizing.width);