feat(ui): add configurable input panel max rows and horizontal scrolling

- Introduce `ui.input_max_rows` (default 5) to control how many rows the input panel expands before scrolling.
- Bump `CONFIG_SCHEMA_VERSION` to **1.2.0** and update migration documentation.
- Update `configuration.md` and migration guide to describe the new setting.
- Adjust TUI height calculation to respect `input_max_rows` and add horizontal scrolling support for long lines.
- Add `unicode-segmentation` dependency for proper grapheme handling.

crates/owlen-tui/src/chat_app.rs

@@ -679,6 +679,11 @@ impl ChatApp {
         &self.theme
     }
 
+    pub fn input_max_rows(&self) -> u16 {
+        let config = self.controller.config();
+        config.ui.input_max_rows.max(1)
+    }
+
     pub fn set_theme(&mut self, theme: Theme) {
         self.theme = theme;
     }
@@ -867,18 +872,9 @@ impl ChatApp {
             }
             Event::Paste(text) => {
                 // Handle paste events - insert text directly without triggering sends
-                if matches!(self.mode, InputMode::Editing) {
-                    // In editing mode, insert the pasted text directly into textarea
-                    let lines: Vec<&str> = text.lines().collect();
-                    for (i, line) in lines.iter().enumerate() {
-                        for ch in line.chars() {
-                            self.textarea.insert_char(ch);
-                        }
-                        // Insert newline between lines (but not after the last line)
-                        if i < lines.len() - 1 {
-                            self.textarea.insert_newline();
-                        }
-                    }
+                if matches!(self.mode, InputMode::Editing | InputMode::Visual)
+                    && self.textarea.insert_str(&text)
+                {
                     self.sync_textarea_to_buffer();
                 }
                 // Ignore paste events in other modes