fix completion verification + perform action on first xpath that can be found on the page

[navidkpr]

why

• Currently we try to find the element from the first xpath fetched. Sometimes we can't use that xpath for the element. Now we check against all xpaths.
• Before we'd scroll down and check for action completion on every step. But we only need to check when action was marked as completed by the LLM

what changed

Covered above

test plan

Evals

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: a8f937aae6f9834f12901ae8afe38d13db855a14

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