fix: reduce background pointer CPU usage

[ostapondo]

What changed, and why

What you ran

Checks

• swift build passes on every commit in the branch, not just the last one
• New logic is covered in App/Tests/plonkTests/ or mcp/test/, or it is not the kind that can be
• Commits use feat: / fix: / docs: / chore: / refactor:
• If this touches the network, the permissions, the entitlements or the update path, README.md and SECURITY.md still tell the truth — fixed in this PR if not
• Screenshots below for anything visual

If this moves windows

Setup: macOS ,

• One screen. Snap into a zone by drag and by ⌃⌥1–⌃⌥9. Both land in the same place.
• Put it back. ⌃⌥0 returns the window to the frame it had before Plonk first touched it.
• A second monitor. A window snapped on each screen stays on its own, and the zone numbers follow the screen the cursor is on.
• Mixed scale factors. A Retina screen beside a 1x one, a window snapped on each. Nothing is half-size or double-size.
• Unplug and plug back in. Windows return to the monitor they were on, not to index 0.
• An excluded app. A window of an app on the exclusions list is left alone by drag and by shortcut, and still moves when an agent names it on purpose.

Before / after from testbench.sh state