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, 7 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e869346..798e8f8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -36,6 +36,13 @@ point at which they are stable.
 
 ### Changed
 
+- The status bar counts threads as they arrive instead of saying "Searching..."
+  until the query is done. On a large query after a reboot, when the notmuch
+  index is still being read from disk, the first rows appear seconds before the
+  walk finishes; the bar used to go on claiming the query was running for all of
+  that time, which made a slow query look like a frozen one. Nothing about the
+  timing changes.
+
 - The dialog reporting configuration problems at startup now appears over the
   main window instead of before it. Which problems interrupt startup is
   unchanged: a keybinding that is being ignored does, a notice such as "no sync