Fix row height clipping and line number column font not updating

[Copilot]

At non-default font sizes, descenders were clipped and the line number column ignored font preference changes entirely.

Changes

• Descender clipping: NSTableView.rowHeight is the total row height; the usable cell drawing rect is rowHeight − intercellSpacing.height. The previous calculation didn't account for this, clipping 1px off top/bottom at default spacing. Row height now includes the intercell spacing:

  self.tableView.rowHeight = MAX(17.0, fontHeight + self.tableView.intercellSpacing.height);

• Line number column font: createLineNumberColumn allocates its own NSTextFieldCell, separate from the dataCell ivar. applyTableFont only updated dataCell, leaving the line number cell at the default font. Fix iterates all columns and updates the line number column's data cell:

  for (NSTableColumn *col in self.tableView.tableColumns) {
      if ([col.identifier isEqualToString:TTLineNumberColumnIdentifier]) {
          [col.dataCell setFont:font];
          break;
      }
  }

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