Log list: resizable columns with a sticky header

The list gets a thin sticky header (received, message time, severity,
host, app, message). Dragging the edge of a header resizes the column,
a double-click returns it to the automatic width; widths are clamped per
column and remembered per browser (logstream.cols.*), and Settings >
Interface has a "Reset column widths" button.

The columns are defined once on a #table wrapper from --col-* variables;
the header and every row use subgrid, so all rows line up (host and app
widths no longer vary from row to row). The wrapper clips with
overflow: clip so that the header can stick under the top bar. Phones
keep the two-line layout without header.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -64,6 +64,12 @@ Severity badges `err`/`crit` and `warning` use the colors of the `error` and `wa
 
 Shortcuts: `/` focuses the search box, `Esc` clears it. Clicking a row shows all its fields.
 
+The column headers stay visible while scrolling. Drag the edge of a header (received, message
+time, severity, host, app) to resize the column, double-click it to go back to the automatic
+width; the message takes the remaining space. Widths are remembered by the browser
+(**Settings > Interface > Reset column widths** restores them all). On phones the list keeps its
+two-line layout without columns.
+
 ## Timeline
 
 The timeline above the list shows the volume of logs per interval, counted by **reception