Improve 'browser_evaluate' for async expressions

[ugulot]

Description

Improve 'browser_evaluate' for async expressions.

Changes to Chrome extension:

• 'Runtime.evaluate' accepts and forwards 'returnByValue' and 'awaitPromise' parameters.

Changes to UnifiedBackend:

• Better detection of function expression;
• Add 'timeout' for async calls.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Smoke tests pass (npm test)
• Manual testing performed
• Tested in MCP client (Claude Desktop, Cursor, etc.)
• Tested extension in Chrome

Test Configuration:

• Node version: v24.14.1
• Chrome version: 146.0.7680.155 (Official Build) (arm64)
• OS: macOS 26.3.1 (25D2128)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• No corresponding changes to the documentation are required
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published