style(table): move the column picker into the table header corner

The show/hide-columns gear only makes sense in table view but sat in the
global toolbar (needing applyColsWrapVisibility to hide it elsewhere). Build
it inside the actions-column header cell in renderTable instead, with inline
handlers (recreated each render, so no dependence on once-wired listeners on
a static node). Removed #colsWrap from the toolbar + the now-obsolete
applyColsWrapVisibility and its callers; kept the menu id so
renderTableColsMenu still populates it, and a live-queried outside-click close.
Added .cols-wrap CSS (was an inline position:relative on the old node).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

css/style.css

@@ -1933,6 +1933,11 @@ input[type="range"]::-webkit-slider-thumb {
 }
 
 /* Table column picker dropdown — only rendered in table view. */
+.cols-wrap {
+    position: relative;        /* anchor for the absolutely-positioned menu */
+    display: inline-flex;
+    vertical-align: middle;
+}
 .cols-menu {
     position: absolute;
     top: calc(100% + 4px);