fix(words): column inserter `+` reveals on hover for non-empty columns

`pointer-events: none` on the inserter wrap (required so caret/text
events pass through to the contenteditable below) ALSO disabled CSS
`:hover` detection — the browser doesn't dispatch `mouseover` to
pointer-events:none elements, so the wrap's `:hover` styles never
fired and the `+` trigger stayed at opacity 0 forever.

Fix: track hover via JS — listen to `mouseenter`/`mouseleave` on the
column elements directly, stash the key in `hoveredColumnKey`, expose
to CSS via `data-hovered` on the wrap. CSS now uses
`[data-words-column-inserter][data-hovered]` instead of `:hover`.

Effect: hovering a non-empty column now reveals the `+` at the bottom
of the column, allowing users to add more blocks below the existing
content. Same fix applied to the empty-column reveal-on-hover (the
opacity-1 boost when fully hovered).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/uix/eidos/components/words/words-column-inserter.svelte

@@ -64,6 +64,7 @@
 
 	let slots = $state<readonly ColumnSlot[]>([]);
 	let openColumnKey = $state<string | null>(null);
+	let hoveredColumnKey = $state<string | null>(null);
 	let raf = 0;
 	// Re-entrancy guard. The dropdown can fire `onSelect` twice in a
 	// row (pointerup + keyboard activation, or a single-click that gets
@@ -152,6 +153,39 @@
 		schedule();
 	});
 
+	// Track which column the mouse is over — `pointer-events: none` on
+	// the inserter wrap is required so caret/text events pass through to
+	// the contenteditable below, but it ALSO disables CSS `:hover`
+	// detection on the wrap (the browser can't dispatch `mouseover` to a
+	// pointer-events:none element). So we listen on the column elements
+	// directly and stash the key in `hoveredColumnKey` — the wrap then
+	// reveals its trigger via `data-hovered={key === hoveredColumnKey}`.
+	$effect(() => {
+		// Re-bind when slots change (so we attach to fresh column elements).
+		void slots;
+		if (!content) return;
+		const cols = Array.from(content.querySelectorAll('[data-words-column]')) as HTMLElement[];
+		const disposers: Array<() => void> = [];
+		for (const col of cols) {
+			const ids = readColumnPath(col);
+			if (!ids) continue;
+			const key = `${ids.columnsIdx}-${ids.colIdx}`;
+			disposers.push(
+				dom.listen(col, 'mouseenter', () => {
+					hoveredColumnKey = key;
+				})
+			);
+			disposers.push(
+				dom.listen(col, 'mouseleave', () => {
+					if (hoveredColumnKey === key) hoveredColumnKey = null;
+				})
+			);
+		}
+		return () => {
+			for (const d of disposers) d?.();
+		};
+	});
+
 	function emptyParagraph(): WordsBlock {
 		return { type: 'paragraph', children: [{ type: 'text', text: '' }] } as WordsBlock;
 	}
@@ -326,6 +360,7 @@
 		<div
 			data-words-column-inserter
 			data-empty={slot.isEmpty ? '' : undefined}
+			data-hovered={hoveredColumnKey === k ? '' : undefined}
 			style="position:absolute; top:{slot.rect.top}px; left:{slot.rect.left}px; width:{slot.rect.width}px; height:{slot.rect.height}px;"
 		>
 			<DropdownMenu
@@ -400,7 +435,8 @@
 		opacity: 0.65;
 		transition: opacity 120ms ease;
 	}
-	[data-words-column-inserter][data-empty]:hover :global([data-words-column-inserter-trigger]),
+	[data-words-column-inserter][data-empty][data-hovered]
+		:global([data-words-column-inserter-trigger]),
 	[data-words-column-inserter][data-empty]
 		:global([data-words-column-inserter-trigger][data-state='open']) {
 		opacity: 1;
@@ -417,14 +453,18 @@
 		opacity: 0;
 		transition: opacity 120ms ease;
 	}
-	[data-words-column-inserter]:not([data-empty]):hover
+	/* `:hover` on the wrap can't fire (wrap has pointer-events: none) so
+	   we drive visibility via `data-hovered` (a JS-tracked attribute set
+	   by listening to `mouseenter`/`mouseleave` on the column elements
+	   themselves — see the matching $effect in the script block). */
+	[data-words-column-inserter]:not([data-empty])[data-hovered]
 		:global([data-words-column-inserter-trigger]),
 	[data-words-column-inserter]:not([data-empty])
 		:global([data-words-column-inserter-trigger][data-state='open']) {
 		pointer-events: auto;
 		opacity: 0.65;
 	}
-	[data-words-column-inserter]:not([data-empty]):hover
+	[data-words-column-inserter]:not([data-empty])[data-hovered]
 		:global([data-words-column-inserter-trigger]:hover),
 	[data-words-column-inserter]:not([data-empty])
 		:global([data-words-column-inserter-trigger][data-state='open']) {