docs(website): expand v10 migration docs and align v9 docs

website/docs/guides/custom-components.mdx

@@ -58,7 +58,7 @@ Custom components allow you to extend DayPicker beyond just using [formatters](.
 | `Dropdown`  | [`DropdownProps`](../api/functions/Dropdown.md)   | Forward `aria-label` and call `onChange` with target. |
 | `Root`      | [`RootProps`](../api/functions/Root.md)           | Forward `rootRef` when `animate` is enabled.          |
 
-The `components` prop accepts a **partial** map—pass only the entries you want to override. The legacy `Button` entry is deprecated; prefer `NextMonthButton` and `PreviousMonthButton`.
+The `components` prop accepts a **partial** map—pass only the entries you want to override.
 
 ## List of Custom Components
 
@@ -89,7 +89,6 @@ The `components` prop accepts a **partial** map—pass only the entries you want
 | [`Weekdays`](../api/functions/Weekdays.md)                       | The row containing the week days.                              |
 | [`Weeks`](../api/functions/Weeks.md)                             | The weeks section in the month grid.                           |
 | [`YearsDropdown`](../api/functions/YearsDropdown.md)             | The dropdown with the years.                                   |
-| `Button`                                                         | Deprecated: use `NextMonthButton`/`PreviousMonthButton`.       |
 
 ## DayPicker Hook
 

website/docs/guides/custom-selections.mdx

@@ -297,15 +297,24 @@ Use `modifiersClassNames` or `modifiersStyles` to surface your custom state (for
 
 ## Week numbers and starts
 
-For week-based selections, set `weekStartsOn` (locale-aware) and consider handling `onWeekNumberClick` to select a week when its number is clicked. Combine it with `showWeekNumber`.
+For week-based selections, set `weekStartsOn` (locale-aware) and use a custom `WeekNumber` component to handle week selection when clicking the week number.
 
 ```tsx
 <DayPicker
   showWeekNumber
   weekStartsOn={1}
-  onWeekNumberClick={(weekNumber, week, e) => {
-    e.preventDefault();
-    setSelectedWeek({ from: week.from, to: week.to });
+  components={{
+    WeekNumber: ({ week, ...thProps }) => (
+      <th
+        {...thProps}
+        onClick={() =>
+          setSelectedWeek({ from: week.days[0].date, to: week.days[6].date })
+        }
+        style={{ cursor: "pointer" }}
+      >
+        {week.weekNumber}
+      </th>
+    ),
   }}
   modifiers={{ selected: selectedWeek }}
 />