Add Gemini agent, tools and cli support, from #169

[alberthu233]

Summary
This PR extracts and contributes the GeminiAgent and Gemini computer-use tool from #169 and made requested changes.

Will add CLI integration for hud eval in a followup commit.

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Note

Introduce a Gemini MCP agent and computer-use tool, integrate it into the CLI eval flow, and add supporting settings, types, tests, and dependency.

• Agents:
  • Add GeminiAgent using Google GenAI with MCP tool execution, tool mapping, screenshot trimming, and function response formatting.
  • Export GeminiAgent in hud/agents/__init__.py.
• Computer Tools:
  • Add GeminiComputerTool mapping Gemini computer-use functions (click_at, navigate, drag_and_drop, etc.) to executor actions with normalized coords and URL metadata.
  • Expose in hud/tools/__init__.py and hud/tools/computer/__init__.py.
• CLI (eval):
  • Add AgentType.GEMINI and integrate Gemini into agent selection, builder, and dataset/single-task flows with default model and API key checks.
  • Update prompts/help text to include Gemini.
• Settings/Types:
  • Add settings.gemini_api_key and Gemini display/rescale defaults in computer_settings.
  • Extend AgentType with gemini.
  • Enhance ContentResult to carry url and emit __URL__: metadata for screenshots.
• Playwright:
  • Guard wait_for_load_state type and reuse existing CDP context/page.
• Dependencies:
  • Add google-genai to pyproject.toml.
• Tests:
  • Add comprehensive tests for GeminiAgent and CLI build_agent for Gemini.

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[Parth220]

Looks good!

Thanks for addressing my changes from #169 and adding CLI suport.

Can you make sure to get ruff check and linting passing before merging?

[cursor]

Bug: Undefined Argument in Constructor Causes Validation Issues

The MCPToolCall constructor is passed a gemini_name argument not defined in its schema, noted by a type: ignore comment. This may cause runtime validation errors or silently drop the field, making subsequent getattr calls fragile.