[WIP - do not merge] Fm/actions not found

[filip-michalsky]

why

Paul mentioned a vision where stagehand will be a tool we can pass to an LLM to perform an action on the web. In that sense, we DO want to return success/ failure signal and a reason for the failure so that the agent/developer can heal their pipelines (either manually or agentically).

what changed

We are returning a success/error from each stagehand method. This slightly changes the API but opens us a route to use stagehand as a tool to pass to LLMs more seamlessly.

test plan

need more evals should be our motto

[filip-michalsky]

not loving the new API - might change back to just throw an action error if action is not performed

[filip-michalsky]

we won't be merge this, reworked at #79