Remove machine mode entirely from g3

- Delete machine_ui_writer.rs
- Remove --machine CLI flag from cli_args.rs
- Remove run_machine_mode(), run_interactive_machine(), run_autonomous_machine() functions
- Remove handle_machine_command() function
- Simplify OutputMode enum to just use SimpleOutput directly
- Simplify SimpleOutput struct (remove machine_mode field)
- Remove machine_mode parameter from setup_workspace_directory()
- Remove test_machine_option_accepted test
- Disable ACD by default in agent_mode (requires --acd flag)
- Change 'memory checkpoint' message formatting
- Remove dehydration status message

crates/g3-cli/src/utils.rs

@@ -67,7 +67,7 @@ pub fn display_context_progress<W: UiWriter>(agent: &Agent<W>, _output: &SimpleO
 
 /// Set up the workspace directory for autonomous mode.
 /// Uses G3_WORKSPACE environment variable or defaults to ~/tmp/workspace.
-pub fn setup_workspace_directory(machine_mode: bool) -> Result<PathBuf> {
+pub fn setup_workspace_directory() -> Result<PathBuf> {
     let workspace_dir = if let Ok(env_workspace) = std::env::var("G3_WORKSPACE") {
         PathBuf::from(env_workspace)
     } else {
@@ -80,7 +80,7 @@ pub fn setup_workspace_directory(machine_mode: bool) -> Result<PathBuf> {
     // Create the directory if it doesn't exist
     if !workspace_dir.exists() {
         std::fs::create_dir_all(&workspace_dir)?;
-        let output = SimpleOutput::new_with_mode(machine_mode);
+        let output = SimpleOutput::new();
         output.print(&format!(
             "📁 Created workspace directory: {}",
             workspace_dir.display()