Accessibility tree omits values for content editing hosts

[enginespot]

Before you start

• I searched existing issues and did not find a duplicate.
• I reproduced this on the current main branch at f449e6f.
• This is not a security vulnerability.

Environment

• Platform: macOS arm64
• Surface: CDP server / embedded obscura-cdp
• Affected area: CDP Accessibility domain
• Build variant: independent of rendering and stealth

Reproduction

1. Load a document containing a content editing host such as <div role="textbox" contenteditable>draft</div>.
2. Request the accessibility tree with Accessibility.getFullAXTree.
3. Find the AX node whose backendDOMNodeId matches the editable element.

The same result can be reproduced directly through obscura-cdp by building AX nodes for a parsed document.

Expected behavior

The AX node for the content editing host exposes its current DOM text as the AX value. Empty editing hosts expose an empty value. Descendants that merely inherit editability do not each expose duplicate values, and a nested host inside a disabled editing region exposes its own value.

Native input, textarea, and select value behavior remains unchanged.

Actual behavior

The element is exposed as a textbox and may be marked editable, but its AX node has no value because value computation only handles native form controls.

Rendering details

Not applicable.

Headless Chrome comparison

Headless Chrome exposes the current value for an editable textbox; obscura currently omits it.