Replace row/col number inputs with graphical grid cell picker

Click a cell in the visual grid to select it. Cell images shown where
available. Selected cell highlighted with accent border.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/style.css

@@ -1504,15 +1504,38 @@ nav {
 	gap: 0.4rem;
 }
 
-.i-grid-coords {
-	display: flex;
-	align-items: center;
-	gap: 0.4rem;
-	font-size: 0.9rem;
+.i-grid-visual {
+	display: grid;
+	gap: 2px;
+	max-height: 320px;
+	overflow-y: auto;
 }
 
-.input-narrow {
-	width: 4rem;
+.igv-cell {
+	position: relative;
+	aspect-ratio: 1;
+	background: var(--surface-raised);
+	border: 2px solid transparent;
+	border-radius: 2px;
+	cursor: pointer;
+	overflow: hidden;
+}
+
+.igv-cell:hover {
+	border-color: var(--accent);
+}
+
+.igv-cell.igv-selected {
+	border-color: var(--accent);
+	box-shadow: inset 0 0 0 1px var(--accent);
+}
+
+.igv-img {
+	width: 100%;
+	height: 100%;
+	object-fit: cover;
+	display: block;
+	pointer-events: none;
 }
 
 /* ===== CELL INVENTORY OVERLAY ===== */