feat(ew): sync layout-mode block & image selection with the doc

[usman-khalid]

Should be merged with adobe/da-nx#605

Implements support to select blocks/images in canvas synced to doc and the outline panel.

• If in split mode, clicking a block in the outline panel scrolls down to it in both doc-mode and canvas.
• Selecting a block in canvas retains the selection in doc-mode (and vice versa)
• Selecting a block in canvas adds it to the chat context, same as doc-mode
• Allows synced image selection between doc-mode and canvas

Screen.Recording.2026-07-15.at.15.48.53.mov

Note on event system consistency: This PR adds one new postMessage pair (set-selected-node / node-select) and one new consumer of the existing editorSelectChange bus. Both follow current conventions, but I'm aware of SITES-46045 and if that lands while this is still open, happy to refactor as needed.

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Commits

• 557fcc6 ✅ (latest)
• af7fff1 ✅

[sharanyavinod]

Thank you for the contribution!

Looks good, just a nit: would be nice to cleanup the comments where possible or make them more concise.