Show the row count while the load is still waiting on it

X-Row-Count is exact but travels with the response headers, and in grain mode
the server aggregates the whole table before sending any -- so the number
appeared just as the fifteen-second wait ended, which is no use to anyone
watching it.

The forecast table's own count goes up first instead, from the same
table-info the status bar already reads, and the exact figure replaces it
when the headers arrive. The count query is deliberately not awaited: it
scans the whole table, and the load must not wait on a progress message.

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

ui/src/views/Forecast.jsx

@@ -57,10 +57,15 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
   const [loading,      setLoading]      = useState(false)
   const [largeDataset, setLargeDataset] = useState(false)
   const [loadProgress, setLoadProgress] = useState(null)  // { received, total }
-  // Rows the server says it is sending, from X-Row-Count. Known as soon as the
+  // Rows the load is waiting on, so the wait can say what it is waiting for --
-  // headers land, well before the body has been read, so the wait can say what
+  // on this data the row count is the wait (see CLAUDE.md, "Load time is
-  // it is waiting for -- on this data the row count is the wait (see CLAUDE.md,
+  // dominated by row count").
-  // "Load time is dominated by row count").
+  //
+  // Filled twice. X-Row-Count is exact but arrives with the response headers,
+  // and in grain mode the server aggregates before sending any: the number
+  // turned up just as the wait ended. So the forecast table's own count goes in
+  // first, from the same table-info the status bar reads, and the exact figure
+  // replaces it when the headers land.
   const [loadRows,     setLoadRows]     = useState(null)
   const [msg,          setMsg]          = useState(null)
 
@@ -646,7 +651,7 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
     if (!r.ok) { const { error } = await r.json(); throw new Error(error || 'Failed to load data') }
     const rowCount = parseInt(r.headers.get('X-Row-Count') || '0')
     const total    = parseInt(r.headers.get('Content-Length') || '0') || null
-    setLoadRows(rowCount || null)
+    if (rowCount) setLoadRows(rowCount)
     const reader   = r.body.getReader()
     const chunks   = []
     let received   = 0
@@ -684,6 +689,12 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
     setLargeDataset(false)
     setLoadProgress(null)
     setLoadRows(null)
+    // deliberately not awaited: it is a count over the whole forecast table and
+    // the load must not wait on it
+    fetch(`/api/versions/${vid}/table-info`)
+      .then(r => r.ok ? r.json() : null)
+      .then(info => { if (info?.rows && initIdRef.current === myId) setLoadRows(n => n ?? info.rows) })
+      .catch(() => {})
     setSlices([])
     setExpandDepth(null)
     adoptSplit([], 0)