[FEATURE]: Element annotation queue with visual markers (Codex-like) #51421

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Related: #26772, #30755, #20543. Those cover a general embedded browser, this one is specifically about the annotation workflow.

Problem: when iterating on UI, describing an element in text ("the second card, the blue button on mobile") is slow and ambiguous.

Proposed workflow in Desktop (V2 browser pane):

1. Load local dev URL in the embedded pane
2. Click an element or drag an area (Annotation mode)
3. Type a comment -> it goes into a per-session annotation queue
4. Each annotation gets a visual number badge on the page (1, 2, 3...) like Codex, with blue outline on selected element
5. Screenshot + DOM context (selector, file/component if resolved) attached to chat as separate items
6. Ask agent to address queue item by item

Why it belongs in OpenCode:

• Removes selector copy-paste between browser and chat
• Keeps DOM + styles + visual state in one place
• Matches Codex / Cursor behavior users already expect
• Builds on top of V2 browser plugin (feat(browser): add a public-API browser plugin #46531) + tabs (feat(desktop): add browser tabs and Chromium diagnostics #44838), just adds the user annotation layer

Keep V1 minimal: select, comment, queue, numbered markers, screenshot-to-chat. No visual editing, no auto-apply.