feat(interaction): add scroll-to-element primitive

[NianJiuZst]

Summary

• add bsk scroll-to <ref-or-selector> backed by the new tool.scroll_to RPC
• resolve snapshot refs and selectors inside the Agent Window, including OOPIF targets, and scroll both frame owners and the target with Chromium CDP
• return the target's visible top-level viewport bounds and integrate dialogs, cancellation, hover release, and the interrupt gate

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --locked -- -D warnings
• cargo test --workspace --locked
• pnpm lint
• extension TypeScript compile, 58 test files / 688 tests, and production build
• node --test scripts/*.test.mjs
• real Chromium probe with the branch-built CLI and unpacked extension in an isolated daemon/profile:
  • before: scrollY=0, target top=2508, viewport 720
  • after bsk scroll-to '#target': scrollY=2178, target top=330, bottom=390, independently verified visible=true