(2/3) Add opt-in accelerated scroll dispatch

[miguelg719]

Summary

• Add opt-in accelerated scrolling via BROWSERBASE_ACCELERATED_SCROLL=true.
• Capture wheel events over the live-view area and dispatch them to the active remote page through CDP.
• Keep the default live-view scroll path unchanged for compatibility with custom scroll implementations.

Stack

• Base: pr-automation-session-endpoint
• Sequenced after automation/session work because it also extends the session and IPC input surfaces.

Verification

• npm run build
• git diff --check