Update CLAUDE.md; add checkbox single selection example

Author: glin

CLAUDE.md

@@ -14,7 +14,7 @@ New in v0.4.5.9000
 
 ## Development Workflow
 
-1. **Update design docs**: When using Plan Mode or for major features, write planning and design docs into the `design/` directory. Use `design/virtual-scrolling/` as a model. Ensure that features consider accessibility (targeting WCAG 2.2 at a minimum) and include a test plan. Also create an Rmd file with examples of different test cases. Use mtcars dataset for examples unless another dataset is more appropriate.
+1. **Update design docs**: When using Plan Mode or for major features, write planning and design docs into the `design/` directory. Use `design/virtual-scrolling/` as a model. Ensure that features consider accessibility (targeting WCAG 2.2 at a minimum) and include a test plan. Also create an Rmd file with examples of different test cases. Use MASS::Cars93 or mtcars datasets for examples unless another built-in R dataset is more appropriate.
 2. **Make changes**
 3. **Document R API**: Run `devtools::document()` in R when making any changes to the R API (roxygen comments).
 4. **Format**: Format JavaScript code using `prettier`.

design/js-row-selection-api/js-row-selection-api-test.Rmd

@@ -674,4 +674,32 @@ tagList(
     elementId = "filtered-table"
   )
 )
+```
+
+### Single selection with custom checkboxes
+
+Expected: Checkboxes work with single selection mode. Clicking a checkbox selects that row and deselects any previously selected row.
+
+```{r}
+reactable(
+  MASS::Cars93[1:6, c("Manufacturer", "Model", "Type", "Price")],
+  selection = "single",
+  onClick = "select",
+  columns = list(
+    # Hide the default selection column
+    .selection = colDef(show = FALSE),
+    # Add a custom checkbox column
+    Manufacturer = colDef(
+      html = TRUE,
+      cell = JS("function(cellInfo) {
+        const checked = cellInfo.selected ? 'checked' : ''
+        return `<label style=\"display: flex; align-items: center; gap: 8px\">
+          <input type=\"checkbox\" ${checked} onclick=\"event.stopPropagation(); cellInfo.toggleRowSelected()\">
+          ${cellInfo.value}
+        </label>`
+      }")
+    )
+  ),
+  elementId = "checkbox-single"
+)
 ```