feat(command): decompose Command.Dialog and fix Escape/separator bugs (#1064)

* feat(command): decompose Command.Dialog and fix Escape/separator bugs

Decompose Command.Dialog into a Root/Trigger/Content compound namespace,
fix Escape key not closing the dialog, fix Command.Separator not
auto-hiding during filtering, and add browser tests covering all three.

* fix preventCloseOnNestedPopupEscape behavior

* fix test

Author: cody-dot-js

.changeset/command-dialog-decompose.md

@@ -0,0 +1,38 @@
+---
+"@ngrok/mantle": patch
+---
+
+Decompose `Command.Dialog` into a `Root`/`Trigger`/`Content` namespace.
+
+**Breaking change**: `Command.Dialog` is now a compound namespace instead of a monolithic component. Migrate existing usage:
+
+```diff
+- <Command.Dialog open={open} onOpenChange={setOpen}>
+-   <Command.Input placeholder="..." />
+-   <Command.List>...</Command.List>
+- </Command.Dialog>
++ <Command.Dialog.Root open={open} onOpenChange={setOpen}>
++   <Command.Dialog.Content>
++     <Command.Input placeholder="..." />
++     <Command.List>...</Command.List>
++   </Command.Dialog.Content>
++ </Command.Dialog.Root>
+```
+
+The new `Command.Dialog.Trigger` sub-component allows opening the dialog from a button without managing `open` state manually:
+
+```tsx
+<Command.Dialog.Root>
+  <Command.Dialog.Trigger asChild>
+    <Button type="button">Open Command Palette</Button>
+  </Command.Dialog.Trigger>
+  <Command.Dialog.Content>
+    <Command.Input placeholder="Type a command or search..." />
+    <Command.List>...</Command.List>
+  </Command.Dialog.Content>
+</Command.Dialog.Root>
+```
+
+Also fixes two bugs:
+- `Command.Dialog` now correctly closes on Escape key press.
+- `Command.Separator` now automatically hides when all adjacent groups are filtered out.