chore: update Playwright.NET to v1.56.1

[lucassc]

This PR updates Playwright.NET to version 1.56.1, a maintenance release that follows 1.56.0.

Changes

• Bump AssemblyVersion from 1.55.0 to 1.56.1
• Maintain DriverVersion at 1.56.1 (already rolled in chore: roll driver to 1.56.1 #3250)
• Docker images will be built with Playwright 1.56.1 drivers

Playwright 1.56.1 Highlights

This is a maintenance release with bug fixes and improvements:

• Fix for local-network-access permission in Chromium
• Improvements to agents (workspaceFolder ref removal from vscode mcp)
• Rename agents to test agents
• Various MCP-related fixes

Related Links

• Playwright 1.56.1 release: https://github.com/microsoft/playwright/releases/tag/v1.56.1
• Playwright 1.56.0 release: https://github.com/microsoft/playwright/releases/tag/v1.56.0
• Driver rolled to 1.56.1: chore: roll driver to 1.56.1 #3250
• v1.56.0 PR: chore: update Playwright.NET to v1.56.0 #3252

Testing

• Docker builds will be validated via CI
• All existing tests should pass with the updated driver version

cc @microsoft/playwright-dotnet-maintainers

[yury-s]

We are handling it as a part of the release.