feat(ui): add real-time metrics updates during typing

- Update display periodically (every 100ms) even without keyboard input
- Ensures elapsed time, WPM, CPM, and other metrics update in real-time
- Applies to all typing screen methods: start_session, show, show_with_state

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

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

Author: unhappychoice

src/game/screens/typing_screen.rs

@@ -177,6 +177,9 @@ impl TypingScreen {
                         }
                     }
                 }
+            } else {
+                // No keyboard event, but update display periodically for real-time metrics
+                self.update_display()?;
             }
         }
 
@@ -233,6 +236,9 @@ impl TypingScreen {
                         }
                     }
                 }
+            } else {
+                // No keyboard event, but update display periodically for real-time metrics
+                self.update_display()?;
             }
         }
 
@@ -277,6 +283,9 @@ impl TypingScreen {
                         }
                     }
                 }
+            } else {
+                // No keyboard event, but update display periodically for real-time metrics
+                self.update_display()?;
             }
         };