feat(BlockEditor): add single block selection via drag handle click

- add `onSelectBlock` prop to Block component wired to drag handle click
- implement `selectBlock` function in BlockEditor to select a single block and clear text selection

src/shared/components/BlockEditor/Block.client.js

@@ -41,6 +41,7 @@ const Block = forwardRef(function Block(
     onSlashOpen,
     onSlashClose,
     onSelectAllBlocks,
+    onSelectBlock,
     onShortcutMatch,
     onFocus,
     onDragStart,
@@ -298,6 +299,7 @@ const Block = forwardRef(function Block(
           tabIndex={-1}
           title="Glisser pour réordonner"
           onMouseDown={handleHandleMouseDown}
+          onClick={() => onSelectBlock?.(block.id)}
           disabled={disabled}
           className="w-5 h-5 flex items-center justify-center rounded text-neutral-500 hover:bg-neutral-200 dark:hover:bg-neutral-700/60 hover:text-neutral-900 dark:hover:text-white text-xs cursor-grab active:cursor-grabbing leading-none"
         >

src/shared/components/BlockEditor/BlockEditor.client.js

@@ -86,6 +86,13 @@ export default function BlockEditor({
     if (document.activeElement instanceof HTMLElement) document.activeElement.blur();
   }
 
+  function selectBlock(id) {
+    setSelectedBlockIds(new Set([id]));
+    const sel = typeof window !== 'undefined' ? window.getSelection() : null;
+    sel?.removeAllRanges();
+    if (document.activeElement instanceof HTMLElement) document.activeElement.blur();
+  }
+
   function deleteSelectedBlocks() {
     if (selectedBlockIds.size === 0) return;
     const next = blocks.filter(b => !selectedBlockIds.has(b.id));
@@ -820,6 +827,7 @@ export default function BlockEditor({
             onSlashOpen={handleSlashOpen}
             onSlashClose={handleSlashClose}
             onSelectAllBlocks={handleBlockSelectAll}
+            onSelectBlock={selectBlock}
             onDragStart={() => setDragOver(null)}
             onDragEnd={handleDragEnd}
             onDragOver={handleDragOver}