fix(cli): wrap ANSI codes in prompt for rustyline compatibility

Rustyline needs ANSI escape codes wrapped in \x01...\x02 markers
to correctly calculate visible prompt length. Without this, tab
completion breaks because rustyline miscalculates cursor position.

crates/g3-cli/src/interactive.rs

@@ -23,6 +23,8 @@ use crate::utils::display_context_progress;
 /// Build the interactive prompt string.
 ///
 /// Format:
+/// Note: ANSI escape codes are wrapped in \x01...\x02 markers for rustyline
+/// to correctly calculate visible prompt length (required for tab completion).
 /// - Multiline mode: `"... > "`
 /// - No project: `"agent_name> "` (defaults to "g3")
 /// - With project: `"agent_name | project_name> "` where `| project_name>` is blue
@@ -36,12 +38,15 @@ pub fn build_prompt(in_multiline: bool, agent_name: Option<&str>, active_project
                 .file_name()
                 .and_then(|n| n.to_str())
                 .unwrap_or("project");
+            // Wrap ANSI codes in \x01...\x02 for rustyline to ignore them in length calculation
+            let blue = format!("\x01{}\x02", SetForegroundColor(Color::Blue));
+            let reset = format!("\x01{}\x02", ResetColor);
             format!(
                 "{} {}| {}>{} ",
                 base_name,
-                SetForegroundColor(Color::Blue),
+                blue,
                 project_name,
-                ResetColor
+                reset
             )
         } else {
             format!("{}> ", base_name)