feat(ux): more refinements

- Custom oneline template (drops timestamp + commit-id hash from the
  left pane); keeps change-id with shortest-unique-prefix highlighting,
  bookmarks, conflict/empty labels, and the description first-line.
  More room for the actually-useful columns.
- Drop the dim '── <change_id> ────' header above the preview; the
  cursor row tee (├) now carries the 'this is what you're looking at'
  signal.
- Box-char frame for the preview pane: top border (┌────) and left
  border (│), with ├ replacing │ on the cursor row to draw the eye
  from picker selection into preview content.
- Dynamic description clipping: the description fills whatever rows
  are left after the file list (ellipsis on overflow). Replaces the
  hard 3-line cap, which under-used vertical space for short file
  lists and was buggy (didn't count blank lines within description).
- Bump VIEWPORT_MIN from 15 to 20 so the preview pane has enough
  vertical room to be useful by default.

src/main.rs

@@ -89,7 +89,7 @@ fn run_pick(subcommand: &str, passthrough: &[String], emit: bool) -> Result<u8>
         None
     };
 
-    let tui_result = tui::run(rows);
+    let tui_result = tui::run(rows, subcommand, passthrough);
 
     if let Some(saved) = saved_stdout {
         restore_stdout(saved)?;