feat: bump acp protocol to 0.12.2

[PsiACE]

Summary

This pull request introduces several improvements and updates across the quickstart documentation, example agents and clients, and the Gemini CLI integration, as well as schema and version updates. The main changes include support for new message and session fields, improved prompt handling (including timeouts), expanded schema methods, and updated documentation to reflect these enhancements.

Key changes:

Protocol and Schema Updates

• Bumped the protocol and schema versions to 0.10.0 for the Python package and v0.12.2 for the schema, reflecting significant feature additions and compatibility updates.
• Expanded the schema (schema/meta.json) to include new agent and client methods such as document events, NES (New Elicitation System) operations, provider management, and elicitation methods.

Message and Session Handling

• Added a message_id parameter to prompt methods in agents and clients, ensuring that user messages can be tracked and correlated throughout the protocol. The PromptResponse now includes the user_message_id field.
• Updated session management methods (new_session, load_session) to accept additional_directories and allow mcp_servers to be optional, improving flexibility for session initialization.

Gemini CLI Example Enhancements

• Enhanced the Gemini CLI example to support timeouts for prompts, cancellation on timeout, and new command-line arguments such as --prompt, --prompt-timeout, --experimental-acp, and --skip-trust.

API and Type Updates

• Updated client and agent examples to use new types and updates, including ToolCallUpdate, ConfigOptionUpdate, SessionInfoUpdate, and UsageUpdate for more comprehensive session and tool call handling.

Documentation Improvements

• Improved the quickstart guide to use the protocol version constant, generate unique message IDs, and clarify Gemini CLI usage (e.g., replacing --experimental-acp with --acp and adding --skip-trust).

These updates collectively improve protocol compliance, usability, and robustness for developers integrating with the Agent Client Protocol and the Gemini CLI.