Cap the row-label width, and never narrow a column

Each group_by level is its own row-header column, so fitting the first to
its longest label pushes the second to start after it — which reads as the
deeper level being indented past the end of the shallower one, and sends the
rest of the pivot off to the right when a label is long.

Capped at 260px, which trades a rare truncation for a sheet that stays
legible. And taking the max with the current width means Fit only ever
widens, so a width set by dragging is not undone by pressing it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/src/views/Forecast.jsx

@@ -1120,11 +1120,25 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
     }
     if (widest.size === 0) return
 
+    // Capped, and never narrowed.
+    //
+    // Each group_by level is its own row-header column, so widening the first to
+    // its longest label pushes the second to start after it — which reads as the
+    // deeper level being indented past the end of the shallower one. Fitting the
+    // widest label exactly is therefore right for the label and wrong for the
+    // sheet, and a long customer name would push the rest of the pivot off to the
+    // right.
+    //
+    // The cap trades a rare truncation for a layout that stays legible. Taking
+    // the max with the current width means Fit never makes a column narrower
+    // than it already is, so a width set by dragging survives.
+    const MAX_ROW_LABEL_W = 260
     const sizes = { ...grid.saveColumnSizes() }
     for (const [idx, w] of widest) {
       // A few px over: canvas metrics and rendered text differ slightly with font
       // fallback and letter-spacing.
-      sizes[idx] = Math.ceil(w + padding + 8)
+      const fitted = Math.min(Math.ceil(w + padding + 8), MAX_ROW_LABEL_W)
+      sizes[idx] = Math.max(fitted, sizes[idx] ?? 0)
     }
     grid.restoreColumnSizes(sizes)
     await grid.draw({ invalid_columns: true })