Add web_view tool: headless browser with text extraction and screenshot ...

- New built-in tool web_view: opens URL in headless Chromium via Playwright,
  strips nav/footer/scripts, returns clean readable text (capped at 20k chars).
  Optional screenshot=true returns a PNG injected into context as an image.
  Handles JS-rendered pages and SPAs (waits for networkidle by default).
- http_request description updated: explicitly says to use web_view for human-
  readable pages, http_request for APIs/JSON/custom auth.
- web_view added to all three profiles.

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