feat: add fullPage parameter to browser_screenshot

[fgonnello-shopify]

Summary

• Playwright's page.screenshot() supports fullPage: true to capture the entire scrollable page, but BrowserMCP doesn't expose this option
• Adds an optional fullPage boolean parameter to the browser_screenshot tool schema (defaults to false for backward compatibility)
• Passes the parameter through to the browser extension via the browser_screenshot socket message

Motivation

Capturing entire scrollable pages currently requires manual scroll-and-stitch workflows. With this change, MCP clients can simply pass fullPage: true to get a full-page screenshot in one call.

Changes

• src/tools/custom.ts: Extends the screenshot tool's argument schema with fullPage (optional boolean, defaults to false), parses it from params, and forwards it in the socket message payload

Test plan

• fullPage omitted or false — behaves identically to current behavior (viewport-only screenshot)
• fullPage: true — captures the full scrollable page
• Existing MCP clients that don't pass fullPage continue to work without changes

Note: The browser extension side will also need to read this parameter and pass it to Playwright's page.screenshot({ fullPage }). This PR covers the MCP server side.

🤖 Generated with Claude Code