Function detect_agent 

pub fn detect_agent(command: &[String]) -> AgentKind

Detect the agent kind from the command argv (FR-1.2).

Rules:

• If command is empty, this is a caller bug → Generic.
• If the basename of command[0] is claude (with optional .exe on Windows), → ClaudeCode.
• If the basename is codex → CodexCli.
• If the basename is gemini → GeminiCli.
• Otherwise → Generic.

A forced --adapter flag bypasses this; the CLI wires that by passing the adapter’s AgentKind directly, so detection only runs for the auto path.