fix: set injected Stagehand cursor position to fixed

[mehtakhil]

why

Previously, the injected Stagehand cursor used position: absolute, which caused it to become misaligned when the page was scrolled. Using position: fixed ensures the cursor stays anchored to the viewport and always follows the pointer, regardless of scrolling. This directly affects CUA agent execution, where accurate cursor position provides visual grounding and prevents the agent from clicking multiple times due to cursor misalignment.

what changed

Changed the injected cursor’s CSS from
cursor.style.position = 'absolute' to cursor.style.position = 'fixed'; in domScripts.js.

test plan

• Verified on a scrollable page that the injected Stagehand cursor remains correctly positioned and follows the pointer during scrolling.