fix: scope passive block focus to keyboard navigation (#10063)

The passive-focus selector for blocks and connection paths lacked the
.blocklyKeyboardNavigation gate that the sibling field and icon selectors
in the same rule already have, so passive block outlines leaked into
mouse-only usage. It also never honored the dropdown/widget-div guard its
own comment promised. Scope it identically to the field/icon selectors.

Closes #10062

Author: microbit-matt-hillsdon

packages/blockly/core/css.ts

@@ -571,6 +571,12 @@ input[type=number] {
 
 /* Passive focus cases: */
 /* Blocks with passive focus except when widget/dropdown div in use. */
+.blocklyKeyboardNavigation:not(
+        :has(
+            .blocklyDropDownDiv:focus-within,
+            .blocklyWidgetDiv:focus-within
+          )
+      )
   .blocklyPassiveFocus:is(
     .blocklyPath:not(.blocklyFlyout .blocklyPath),
     .blocklyHighlightedConnectionPath