Dialog captures the wrong trigger when focusable content mounts on open

## Version

`@astryxdesign/core@0.5.0`

## Problem

A controlled `Dialog` can restore focus to `` instead of its opener when its content is mounted only while `isOpen` is true.

`DialogHeader` runs a child `useEffect` that focuses its heading on mount. React runs that child effect before the parent `Dialog` effect that assigns `triggerElementRef.current = document.activeElement`. The dialog therefore captures its own heading (or another newly mounted autofocus child), not the external trigger. If the closed state removes/sanitizes that content, the captured node is detached before close restoration.

`DialogHeader` also focuses its heading when mounted under a closed Dialog because its `shouldAutoFocus` check only excludes inline mode, not `isOpen === false`.

## Minimal shape

```tsx
setOpen(true)}>Open

{open ? (
} content={...} />
) : null}

```

1. Focus and activate `Open`.
2. Close with Escape or `onOpenChange(false)`.
3. Focus lands on `body`, not `Open`.

This shape is useful when a closed dialog must not retain a sensitive payload in the DOM.

## Expected

The Dialog captures the external active element before descendant mount/autofocus effects, and restores that element after the controlled `true -> false` transition. `DialogHeader` should not focus while the parent Dialog is closed.

Potential directions: capture the rising-edge trigger before passive descendant effects, expose `isOpen` in `DialogContext`, and make the header title the Dialog's supported `data-autofocus` target rather than running an unconditional mount effect.

Start with the controlled Dialog and DialogHeader focus and effect behavior described in the issue, then reproduce the minimal conditional-mounting shape with the Escape close path. Verify that the external opener is captured before descendant autofocus effects, restored after the true-to-false transition, and that a closed DialogHeader does not focus; the issue's potential directions identify the relevant context and autofocus areas to investigate.

Written by the indexing model from the issue text.