perf: optimize and verify scrollintoview ref path

[thymikee]

Summary

Optimize and harden scrollintoview @ref behavior on iOS.

• add a geometry planner module for viewport inference + swipe plan computation
• execute ref scrolling via a single swipe-series command instead of repeated per-swipe lookups
• add one post-scroll verification snapshot and fail when the target remains outside the viewport safe band
• keep replay-healing metadata (selectorChain/refLabel) in recorded actions
• document the scrollintoview <text|@ref> behavior and examples

Validation

• pnpm typecheck
• pnpm test:unit
• pnpm test:smoke

[github-actions]

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