feat(codex): support execpolicy approvals and MCP tool calls

[OrdinarySF]

Summary

• Extend Codex permission flow to support execpolicy amendments and newer elicitation response formats.
• Improve Codex MCP client compatibility across CLI versions and capture richer tool-call context.
• Surface MCP tool calls and results in the CLI session stream.

Changes

• Add approved_execpolicy_amendment decision handling across ACP, API types, Codex/Gemini permission handlers, and mapping logic.
• Upgrade Codex MCP client to parse version info, choose MCP subcommand, and emit correct elicitation response shape (decision vs action+decision).
• Capture proposed_execpolicy_amendment from MCP notifications and include it in exec approval inputs.
• Support patch-approval elicitation payloads with message/reason/grantRoot/changes inputs.
• Emit MCP tool-call begin/end events to the frontend using mcp__ naming.

Notes

• Default elicitation style is both when version parsing fails; override via HAPPY_CODEX_ELICITATION_STYLE.
• Continue-session calls now pass conversationId only.