fix(tui): use char-level wrapping instead of word-level for log lines

crates/tui/src/app.rs

@@ -3,6 +3,45 @@ use std::time::Instant;
 
 use log_viewer_core::io::file_reader::FileReader;
 
+/// Split a line into chunks of exactly `width` characters (display columns).
+/// For a log viewer, we want character-level wrapping, not word-level.
+fn wrap_line_chars(line: &str, width: usize) -> Vec<String> {
+    if width == 0 {
+        return vec![String::new()];
+    }
+    if line.is_empty() {
+        return vec![String::new()];
+    }
+    let mut result = Vec::new();
+    let mut row = String::new();
+    let mut col = 0;
+    for ch in line.chars() {
+        let w = if ch == '\t' { 4 } else { 1 };
+        if col + w > width && !row.is_empty() {
+            result.push(std::mem::take(&mut row));
+            col = 0;
+        }
+        if ch == '\t' {
+            row.push_str("    ");
+            col += 4;
+        } else {
+            row.push(ch);
+            col += w;
+        }
+        if col >= width {
+            result.push(std::mem::take(&mut row));
+            col = 0;
+        }
+    }
+    if !row.is_empty() {
+        result.push(row);
+    }
+    if result.is_empty() {
+        result.push(String::new());
+    }
+    result
+}
+
 pub struct App {
     pub should_quit: bool,
 
@@ -77,8 +116,7 @@ impl App {
 
         for i in 0..line_count {
             let line = self.get_line(i).unwrap_or("");
-            let wrapped: Vec<std::borrow::Cow<'_, str>> = textwrap::wrap(line, width);
-            let wrapped: Vec<String> = wrapped.into_iter().map(|c| c.into_owned()).collect();
+            let wrapped = wrap_line_chars(line, width);
             let height = wrapped.len().max(1);
             self.wrap_cache.push(wrapped);
             self.visual_heights.push(height);