feat: implement waitFor tool

[shadowusr]

What's done?

• Refactored element location API. Now it's a discriminated union with two available strategies.
• Implemented a new waitFor tool, which allows agent to wait until some element appears or disappears.
• navigate tool now uses openAndWait instead of url.
• When testing-library query fails with "multiple elements found" error we no longer return the whole error message that includes unoptimized html markup. We return only the first line of the error which includes summary, e.g. "multiple elements with role button and name X were found"

[sipayRT]

console.error?

${actionDescription} successfully

shouldn't it be in the past tense?

[shadowusr]

console.error is used to output debug logs.

MCP servers have two ways of communication as of now — stdio and server sent events. we use stdio as a simple and effective way for a local server. In this case, communication with client is performed via stdout interface, so we can't do any console.logs. And stderr can be used for debug logging.