fix: set topbar menus to non-modal so they dismiss on canvas interaction (#10310)

## Summary

Set topbar menus to non-modal so they dismiss when clicking
inputs/textareas inside nodes with Nodes 2.0 enabled.

## Changes

- **What**: Add `:modal="false"` to `ContextMenuRoot` in WorkflowTab and
`DropdownMenuRoot` in WorkflowActionsDropdown.

![Kapture 2026-03-19 at 23 50
43](https://github.com/user-attachments/assets/f423f3df-48d0-42c4-b2bc-d19feffb9028)


## Review Focus

Modal reka-ui menus set `body.pointer-events: none` and prevent
`focusOutside` dismissal. With Nodes 2.0, widget components use
`@pointerdown.capture.stop` to prevent node dragging, which also blocks
reka-ui's document-level outside-click detection. Non-modal menus allow
`focusin`-based dismissal, which is unaffected by pointerdown stopping.

## Testing

An E2E regression test for this fix requires Nodes 2.0 to be explicitly
enabled (feature-flag guarded), opening a specific topbar menu, and then
clicking inside a canvas node's textarea — an interaction sequence that
has no existing Playwright fixture/helper pattern in the codebase; the
fix itself is a one-line :modal="false" attribute change on reka-ui
primitives whose behavior is documented and tested upstream.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10310-fix-set-topbar-menus-to-non-modal-so-they-dismiss-on-canvas-interaction-3286d73d3650815287d1c66c6ffd4814)
by [Unito](https://www.unito.io)

Co-authored-by: Amp <amp@ampcode.com>

src/components/common/WorkflowActionsDropdown.vue

@@ -80,7 +80,11 @@ const tooltipPt = {
 </script>
 
 <template>
-  <DropdownMenuRoot v-model:open="dropdownOpen" @update:open="handleOpen">
+  <DropdownMenuRoot
+    v-model:open="dropdownOpen"
+    :modal="false"
+    @update:open="handleOpen"
+  >
     <slot name="button" :has-unseen-items="hasUnseenItems">
       <div
         class="pointer-events-auto inline-flex items-center rounded-lg bg-secondary-background"

src/components/topbar/WorkflowTab.vue

@@ -1,5 +1,5 @@
 <template>
-  <ContextMenuRoot>
+  <ContextMenuRoot :modal="false">
     <ContextMenuTrigger as-child>
       <div
         ref="workflowTabRef"