feat(sdk): add actions.scrollTo(target) for extensions

[mhaack]

Summary

• Adds actions.scrollTo(target) to DA_SDK (nx/utils/sdk.js), letting BYO-plugin extensions ask the host editor to scroll to/select a block, content item, or section.
• target is { type: 'block', blockIndex }, { type: 'section', sectionIndex }, or { type: 'content', proseIndex, kind } — posted as { action: 'scrollTo', details: target }, matching the existing fire-and-forget pattern of sendText/setHref/setHash/closeLibrary/showPanel.
• Pairs with adobe/da-live's PR #1286 (adds the host-side handler that receives this message). Both sides are additive and inert alone — this action is unreachable without the da-live handler, and vice versa nothing breaks if either ships first.

Test plan

• Unit tests added covering all three target shapes (test/nx/utils/sdk.test.js)
• Full unit suite green: 1555 passed, 0 failed

🤖 Generated with Claude Code

[aem-code-sync]

Hello, I'm the AEM Code Sync Bot and I will run some actions to deploy your branch.
In case there are problems, just click the checkbox below to rerun the respective action.

• Re-sync branch

Commits

• fdbec31 ✅ (latest)
• 529e11c ✅