test(processes): pan within the table's own range

columns_pan_with_horizontal_scroll set scroll_x to a fixed 40 px. Since
the process table's columns became as wide as their content (lay_row),
the table can pan only 39.28 px, so the scroll was clamped and the
columns moved by 39.28, failing the exact assertion though every column
moved by the same amount. The test now pans by half of max_scroll_x.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

 src/pages/processes.rs | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/pages/processes.rs b/src/pages/processes.rs
index f7c3821..80daaf8 100644
--- a/src/pages/processes.rs
+++ b/src/pages/processes.rs
@@ -729,13 +729,17 @@ mod tests {
         };
         let pc0 = view(&mut state, 10.0, 20.0, 500.0, 400.0, false, &sec_focused, &mut layout, &mut ctx);
         let x0 = header_x(&pc0, "MEM %");
-        // Content (650) is wider than the ~500px page, so the list is
-        // h-scrollable; pan and every column shifts left by exactly that.
+        // The columns are wider than the ~500px page, so the list is
+        // h-scrollable; pan within its range (the columns are as wide as
+        // their content, so the range is the table's, not a fixed figure)
+        // and every column shifts left by exactly that.
         assert!(state.cpu_list.h_scroll_active());
-        state.cpu_list.scroll_x = 40.0;
+        let pan = state.cpu_list.max_scroll_x() / 2.0;
+        assert!(pan > 0.0);
+        state.cpu_list.scroll_x = pan;
         let pc1 = view(&mut state, 10.0, 20.0, 500.0, 400.0, false, &sec_focused, &mut layout, &mut ctx);
-        assert_eq!(header_x(&pc1, "MEM %"), x0 - 40.0);
-        assert_eq!(header_x(&pc1, "CPU %"), header_x(&pc0, "CPU %") - 40.0);
+        assert_eq!(header_x(&pc1, "MEM %"), x0 - pan);
+        assert_eq!(header_x(&pc1, "CPU %"), header_x(&pc0, "CPU %") - pan);
     }
 
     #[test]