review(p9-fb-10): 회차 2 지적 반영

- TAGS_COL_W const 추출 (truncate + pad 동시 사용 — drift 방지).
- format_doc_row 직접 unit test 2개 (Hangul title / Hangul tag) 가
  display column 정렬을 정확히 pin. `<title_w$>` 으로 되돌리는
  회귀가 unit-level 에서 catch 됨.

crates/kebab-tui/src/library.rs

@@ -17,6 +17,11 @@ use ratatui::widgets::{Block, Borders, List, ListItem, ListState, Paragraph};
 use crate::app::{App, KeyOutcome, Pane};
 use crate::input::{display_width, truncate_to_display_width};
 
+/// Width (in display columns) of the `tags` column in the doc-list
+/// row. Used twice — truncate input + pad calculation — so a const
+/// keeps them in sync.
+const TAGS_COL_W: usize = 12;
+
 /// Internal state owned by `LibraryState`. Public-by-crate so
 /// `handle_key_library` can mutate it without crossing the
 /// `pub`-visibility boundary `LibraryState` exposes.
@@ -193,7 +198,7 @@ pub(crate) fn format_doc_row(d: &DocSummary, title_w: usize) -> String {
     } else {
         d.tags.join(",")
     };
-    let tags = truncate_to_display_width(&tags, 12);
+    let tags = truncate_to_display_width(&tags, TAGS_COL_W);
     let updated = d
         .updated_at
         .format(&time::format_description::well_known::Rfc3339)
@@ -206,7 +211,7 @@ pub(crate) fn format_doc_row(d: &DocSummary, title_w: usize) -> String {
     // from `display_width`, then concatenate — the truncate above
     // already guarantees `display_width(title) <= title_w`.
     let title_pad = title_w.saturating_sub(display_width(&title));
-    let tags_pad = 12usize.saturating_sub(display_width(&tags));
+    let tags_pad = TAGS_COL_W.saturating_sub(display_width(&tags));
     format!(
         "{title}{:title_pad$}  {tags}{:tags_pad$}  {updated_short:<10}  {chunk_count}",
         "",
@@ -404,3 +409,56 @@ pub(crate) fn refresh_docs(state: &mut App) -> anyhow::Result<()> {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use kebab_core::{
+        ChunkerVersion, DocSummary, DocumentId, Lang, ParserVersion, SourceType, TrustLevel,
+        WorkspacePath,
+    };
+    use time::OffsetDateTime;
+
+    fn doc(title: &str, tags: &[&str]) -> DocSummary {
+        DocSummary {
+            doc_id: DocumentId("a".repeat(32)),
+            doc_path: WorkspacePath::new("x.md".into()).unwrap(),
+            title: title.into(),
+            lang: Lang("en".into()),
+            tags: tags.iter().map(|s| (*s).into()).collect(),
+            trust_level: TrustLevel::Primary,
+            source_type: SourceType::Note,
+            byte_len: 1,
+            chunk_count: 1,
+            created_at: OffsetDateTime::from_unix_timestamp(1_700_000_000).unwrap(),
+            updated_at: OffsetDateTime::from_unix_timestamp(1_700_000_000).unwrap(),
+            parser_version: ParserVersion("p".into()),
+            chunker_version: ChunkerVersion("c".into()),
+        }
+    }
+
+    /// p9-fb-10: format_doc_row pads by display width (not char
+    /// count) so wide-char titles don't shift downstream columns.
+    /// Regression pin — `<title_w$>` (std::fmt char-count form)
+    /// would fail this for any Hangul title.
+    #[test]
+    fn format_doc_row_pads_by_display_width_for_hangul_title() {
+        let row = format_doc_row(&doc("러스트로 만드는 KB", &["rust"]), 30);
+        // Expected layout (display cols):
+        //   title 30  +  "  "(2)  +  tags 12  +  "  "(2)  +  date 10  +  "  "(2)  +  chunk
+        // chunk = "1" → 1 col. Total = 30+2+12+2+10+2+1 = 59.
+        assert_eq!(
+            display_width(&row),
+            59,
+            "row must align to display columns, not char count: {row:?}"
+        );
+    }
+
+    /// p9-fb-10: Hangul tag also pads by display width.
+    #[test]
+    fn format_doc_row_pads_by_display_width_for_hangul_tag() {
+        let row = format_doc_row(&doc("ascii", &["한글"]), 20);
+        // title 20 + "  " + tags 12 + "  " + date 10 + "  " + "1" = 49
+        assert_eq!(display_width(&row), 49, "row: {row:?}");
+    }
+}