fix(startup): let startup_query name a built-in filter, and run it

Two defects, both reachable only after item 93.

startupSavedQuery() searched the saved queries alone, so a startup_query of
"Inbox" matched nothing once Inbox shipped as a built-in filter and the
duplicated entry was removed from queries.json. It then fell back to
m_savedQueries.first(), which is an arbitrary choice that used to look
reasonable while every install carried an Inbox entry: with the duplicates gone
it opened on a leftover search for one sender, and an empty queries.json opened
on nothing at all. The search now covers the saved queries first, so the user's
own entry wins a name collision, then the built-in filters; the fallback is the
Unread filter, which is always present.

The default startup name has always been "Unread" and now resolves for the
first time: before this it named nothing unless the user happened to have such
an entry.

The constructor also read startup.query directly, and a generated entry stores
no query at all, so even a matching filter opened an empty bar. It resolves
through Config::resolvedQuery() now, unscoped, since the account dropdown
starts on "All accounts".

Icons per the user's choices: a star for Important rather than the flag
action's own icon, since on the query row an icon reads as a category rather
than as an instruction, and mail-folder-sent rather than mail-sent.

Three tests changed rather than adapted, because their premises were the
defect. Two asserted the first-saved-query fallback.
aCronSyncDoesNotRefreshBeforeAnyQueryHasRun assumed a fresh window had run no
query, which is no longer true; it is now
aCronSyncRefreshesTheLastRunQueryNotTheQueryBar and asserts the property that
actually matters on a cron timer, through a new lastRunQueryForTesting() seam,
since a legitimate refresh bumps the generation and the counter cannot tell the
two apart.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/mainwindow.h b/src/mainwindow.h
index bb1ba75..03f21bb 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -186,6 +186,14 @@ public:
     /// stale, so a test standing in for the worker has to know the current one.
     quint64 currentGenerationForTesting() const { return m_generation; }
 
+    /// The query the visible list was actually built from.
+    ///
+    /// A test seam: a refresh re-runs THIS, never the text in the query bar,
+    /// and the difference is only observable through the value itself. The
+    /// generation counter cannot stand in for it, since a legitimate refresh
+    /// bumps the generation too.
+    QString lastRunQueryForTesting() const { return m_lastQuery; }
+
     /// Puts the window into the state refreshCurrentQuery() leaves it in, and
     /// returns the generation the refresh's replies must carry.
     ///