feat: implement ACP for Gemini and migrate to new logic

[ereslibre]

Enable ACP (Agent Communication Protocol) support for Gemini by leveraging the native --experimental-acp flag in the Gemini CLI. This continues the ACP migration by adding Gemini alongside Claude as an ACP-enabled tool.

Related: #405

Changes

• Added Gemini to the ACP-enabled tools list in the run command
• Implemented getACPSpawnCommand() case for Gemini using the native --experimental-acp flag
• Removed the legacy recoverFromError() method from GeminiAgent as ACP handles error recovery differently
• Removed containsGeminiYoloWarning() utility and its associated tests (no longer needed with ACP mode)
• Updated test script to use --passWithNoTests flag since agent tests were removed

Notes

The Gemini CLI natively supports ACP via the --experimental-acp flag, unlike Claude which requires the @zed-industries/claude-code-acp package. This simplifies the Gemini integration significantly.