fix(ribbon): clear blue tool state when its popup window closes (#40)

A ribbon tool that opens a popup window (LAYERS, PAGESETUP,
ABOUT, the style managers, …) marks itself blue via
\`activate_tool\` when the user clicks it, but nothing un-marked
the tool after the window was dismissed — \`OsWindowClosed\`
cleared the matching \`_window\` slot, the active-tool string
stayed put, and the button kept rendering as if the panel were
still open.

Add \`Ribbon::deactivate_tool_if(id)\` (clears only when the
active tool matches) and call it for every popup-window slot in
\`OsWindowClosed\`. Also clear inside the \`ToggleLayers\` close
branch — that path \`take()\`s \`layer_window\` to \`None\` before
\`OsWindowClosed\` fires, so the conditional in the
\`OsWindowClosed\` handler would miss the close otherwise.

Mapped IDs match the matching ribbon \`ToolDef.id\`s (LAYERS,
PAGESETUP, ABOUT) plus command names for the popups normally
opened via the command line (TEXTSTYLE, TABLESTYLE, MLSTYLE,
LAYOUTMANAGER / LAYOUTPANEL, PLOTSTYLE / STYLESMANAGER, DIMSTYLE,
SHORTCUTS / KEYBOARD) so a future ribbon tool with one of those
ids gets the same correct deactivate.

Closes #40

src/ui/ribbon/mod.rs

@@ -144,6 +144,15 @@ impl Ribbon {
     pub fn deactivate_tool(&mut self) {
         self.active_tool = None;
     }
+    /// Clear `active_tool` only when it currently equals `id`. Used by the
+    /// window-close path to deactivate the tool that owned a popup window
+    /// without disturbing a different tool the user picked in the
+    /// meantime. See #40.
+    pub fn deactivate_tool_if(&mut self, id: &str) {
+        if self.active_tool.as_deref() == Some(id) {
+            self.active_tool = None;
+        }
+    }
     pub fn set_wireframe(&mut self, w: bool) {
         self.wireframe = w;
     }