feat(browser): declarative browser action connectors (#33)

Closes #33

Adds seven declarative browser connectors backed by a shared Playwright JS
script generator: browser/navigate, browser/click, browser/fill,
browser/extract, browser/screenshot, browser/wait, browser/evaluate.

Session state (cookies, localStorage, current URL) is serialized to a
session_state blob on output and restored on input, enabling stateful
multi-step browser automation without persistent containers. All connectors
delegate to the existing DockerRunConnector pipeline — no new infrastructure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people