fix(status): count threads as they arrive instead of "Searching..."

Item 74. runQuery() set the status bar once and only queryFinished cleared
it, so the bar kept claiming a query was running for the whole walk while
rows were visibly arriving behind it. Measured cold against a 1.1 GB index:
the first batch reaches the model at 642 ms and the walk finishes at 5714 ms,
so five seconds of a slow query read as a frozen one.

onThreadsReady now sets the bar from the model's own row count after each
batch, which is the number of rows the user can actually see. No timing
changes; this only stops the bar from lying.

The refresh branch returns before the new line, so a background refresh stays
silent exactly as onQueryFinished already keeps it. That silence has its own
test, which fails when the write is moved above the guard.

beginRefreshForTesting() is a new seam: refreshCurrentQuery() returns early
without a worker and a bare window has none, so a test cannot otherwise reach
the refresh path.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/mainwindow.h b/src/mainwindow.h
index d861d72..80c7d2b 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -186,6 +186,19 @@ public:
     /// stale, so a test standing in for the worker has to know the current one.
     quint64 currentGenerationForTesting() const { return m_generation; }
 
+    /// Puts the window into the state refreshCurrentQuery() leaves it in, and
+    /// returns the generation the refresh's replies must carry.
+    ///
+    /// A test seam, because refreshCurrentQuery() returns early without a
+    /// worker and a bare window has none. It sets only what decides whether a
+    /// batch is a refresh's, not what the real function asks the worker to do.
+    quint64 beginRefreshForTesting()
+    {
+        m_refreshGeneration = ++m_generation;
+        m_refreshThreads.clear();
+        return m_refreshGeneration;
+    }
+
     /// The generation a database-stats reply must carry to be accepted.
     ///
     /// A test seam, for the same reason as the one above: onDatabaseStatsReady