Fix text positioning by calculating visual width without ANSI codes

The motion effects were appearing with incorrect row offsets because
the text width calculation included ANSI color escape sequences in
the byte length, causing misaligned centering.

Changes:
- Added utils/ansi.rs module with strip_ansi() and visual_width()
- Updated renderer to use visual_width() for offset positioning
- Updated TerminalManager::print_centered() to use visual_width()
- All text positioning now correctly ignores ANSI escape sequences

This fixes the "shifted in the rows" issue where colored text was
not properly centered due to escape sequence byte counts.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/utils/ansi.rs

@@ -0,0 +1,54 @@
+/// Strip ANSI escape sequences from a string to get visual width
+pub fn strip_ansi(text: &str) -> String {
+    let mut result = String::new();
+    let mut chars = text.chars().peekable();
+
+    while let Some(ch) = chars.next() {
+        if ch == '\x1b' {
+            // Skip ANSI escape sequence
+            if chars.peek() == Some(&'[') {
+                chars.next(); // consume '['
+                // Skip until we hit a letter (the command character)
+                while let Some(&c) = chars.peek() {
+                    chars.next();
+                    if c.is_ascii_alphabetic() {
+                        break;
+                    }
+                }
+            }
+        } else {
+            result.push(ch);
+        }
+    }
+
+    result
+}
+
+/// Get the visual width of a string (excluding ANSI codes)
+pub fn visual_width(text: &str) -> usize {
+    strip_ansi(text).chars().count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_strip_ansi() {
+        let text = "\x1b[38;2;255;87;51mHello\x1b[0m";
+        assert_eq!(strip_ansi(text), "Hello");
+    }
+
+    #[test]
+    fn test_visual_width() {
+        let text = "\x1b[38;2;255;87;51mHi\x1b[0m";
+        assert_eq!(visual_width(text), 2);
+    }
+
+    #[test]
+    fn test_no_ansi() {
+        let text = "Plain text";
+        assert_eq!(strip_ansi(text), "Plain text");
+        assert_eq!(visual_width(text), 10);
+    }
+}