feat(ribbon): Block Palette button reflects panel open state

The Insert tab's Block Palette button now behaves like the View tab toggles
(UCS Icon, View Cube, Ortho, Properties, File Tabs, Layout Tabs): it stays
highlighted while the block palette panel is open and clears when closed.

The Ribbon gains a show_block_palette flag with a set_block_palette setter,
fed into ToggleState and mapped in is_active_tool for the BLOCKPALETTE tool
id. show_block_palette on the app remains the single source of truth; both
mutation paths now mirror it onto the ribbon:

- BLOCKPALETTE / BLOCKSPALETTE command toggles ribbon state alongside the
  panel (src/app/commands/blocks.rs).
- Closing the panel via the dock rail close button clears the ribbon state,
  matching how Close(Properties) already syncs (src/app/update/dialog.rs).

src/app/commands/blocks.rs

@@ -486,6 +486,7 @@ impl OpenCADStudio {
             // BLOCKPALETTE / BLOCKSPALETTE — toggle the docked Insert Block panel.
             "BLOCKPALETTE" | "BLOCKSPALETTE" => {
                 self.show_block_palette ^= true;
+                self.ribbon.set_block_palette(self.show_block_palette);
                 if self.show_block_palette {
                     // Always open expanded so the panel is immediately usable;
                     // the user can still collapse it via the pin (Auto) button.

src/app/update/dialog.rs

@@ -597,6 +597,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                 match id {
                     PanelId::BlockPalette => {
                         self.show_block_palette = false;
+                        self.ribbon.set_block_palette(false);
                         self.block_palette.placing = None;
                     }
                     PanelId::Properties => {

src/ui/ribbon/mod.rs

@@ -50,6 +50,9 @@ pub struct Ribbon {
     pub show_ucs_icon: bool,
     /// Properties panel (PROPERTIES) visibility — drives the Properties button highlight.
     pub show_properties: bool,
+    /// Block Palette panel (BLOCKPALETTE) visibility — drives the Block Palette
+    /// button highlight.
+    pub show_block_palette: bool,
     /// File tabs (FILETAB) visibility — drives the File Tabs button highlight.
     pub show_file_tabs: bool,
     /// Layout tabs (LAYOUTTAB) visibility — drives the Layout Tabs button highlight.
@@ -158,6 +161,7 @@ impl Ribbon {
             show_viewcube: true,
             show_ucs_icon: true,
             show_properties: true,
+            show_block_palette: false,
             show_file_tabs: true,
             show_layout_tabs: true,
             open_dropdown: None,
@@ -311,6 +315,9 @@ impl Ribbon {
     pub fn set_properties(&mut self, on: bool) {
         self.show_properties = on;
     }
+    pub fn set_block_palette(&mut self, on: bool) {
+        self.show_block_palette = on;
+    }
     pub fn set_file_tabs(&mut self, on: bool) {
         self.show_file_tabs = on;
     }
@@ -325,6 +332,7 @@ impl Ribbon {
             show_viewcube: self.show_viewcube,
             show_ucs_icon: self.show_ucs_icon,
             show_properties: self.show_properties,
+            show_block_palette: self.show_block_palette,
             show_file_tabs: self.show_file_tabs,
             show_layout_tabs: self.show_layout_tabs,
         }

src/ui/ribbon/widgets.rs

@@ -37,6 +37,7 @@ pub(super) struct ToggleState {
     pub show_viewcube: bool,
     pub show_ucs_icon: bool,
     pub show_properties: bool,
+    pub show_block_palette: bool,
     pub show_file_tabs: bool,
     pub show_layout_tabs: bool,
 }
@@ -359,6 +360,7 @@ pub(super) fn is_active_tool(
         "NAVVCUBE" => state.show_viewcube,
         "UCSICON" => state.show_ucs_icon,
         "PROPERTIES" => state.show_properties,
+        "BLOCKPALETTE" => state.show_block_palette,
         "FILETAB" => state.show_file_tabs,
         "LAYOUTTAB" => state.show_layout_tabs,
         id => active_tool.as_deref() == Some(id),