feat(filters): put the four built-in filters on the query row

Item 93, the UI half. Unread, Inbox, Flagged and Sent are buttons the
application ships, sitting first on the row, ahead of the user's pinned saved
queries.

runFilter() is runSavedQuery()'s opposite in the one way that matters: it READS
the account box and never writes it. That is item 90's defect. A filter narrows
what the user is already looking at, so the dropdown is its input rather than
something it resets on the way past. A saved query keeps setting the account
from what it stored, because it is a destination and states its own scope.

runQuery() gains an AccountScope parameter. A filter's text arrives already
resolved in the selected account's scope, and scoping it again would put
path:"work/Sent/**" inside path:"work/**".

Two migration changes, both of which unpin rather than delete:

- Sent is no longer migrated from the INI into queries.json. The built-in
  filter covers it, and migrating one too would put two Sent buttons on the
  row, one editable and one not.
- A stored entry naming a known generator is unpinned on load, which is what
  every install upgraded through 0.19.0 carries. It keeps its name and its
  generator and moves to the menu. Deleting it would be data loss on a file
  whose readers are supposed to preserve what they do not own.

The test suite needed the same distinction the design makes.
savedQueryButtonLabels() now skips the filters, and savedQueryButton(window,
label) replaces five positional row->findChild<QPushButton *>() lookups that
were silently returning Unread.

One rendering probe had to be fixed rather than adapted.
replyRowsKeepTheirTextUnderTheThreadLine resized the window to 300px, and four
more buttons pushed the reply row below the viewport: the pixel loop then ran
zero times and reported "0 pixels, the row was painted over", which is a
different defect from the one it exists to catch. It gets 600px and a guard
asserting the row is really inside the viewport, so the next person to shrink
it gets told the truth. Verified by putting 300 back: the guard names the row
at 83..165 in an 82px viewport.

1 files changed, 21 insertions, 15 deletions

diff --git a/src/config.cpp b/src/config.cpp
index 0b65053..ece1fb9 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -482,22 +482,16 @@ void Config::loadSavedQueries(const QString &configPath, QSettings &settings)
         }
         settings.endGroup();
 
-        // Sent was a hardcoded button beside the saved queries and becomes an
-        // ordinary row here, so it can be reordered, renamed, unpinned or
-        // removed like any other. It stays GENERATED, so it still follows the
-        // accounts. Appended last, where the button already sat.
+        // Sent is NOT migrated into queries.json any more. It used to become an
+        // ordinary saved query here, so the hardcoded button could be
+        // reordered, renamed or removed; item 93 makes it one of four built-in
+        // filters instead, which are shipped rather than stored. Migrating it
+        // as well would put two Sent buttons on the row, one of them the user's
+        // to edit and one not.
         //
-        // Only when an account actually configures a sent folder: the button
-        // was hidden entirely otherwise, and migrating a row that always finds
-        // nothing would be worse than what it replaces.
-        if (!allSentQuery().isEmpty()) {
-            SavedQuery sent;
-            sent.name = QStringLiteral("Sent");
-            sent.generated = QStringLiteral("sent");
-            sent.pinned = true;
-            sent.flat = true;
-            m_savedQueries.append(sent);
-        }
+        // Nothing is lost: the built-in Sent resolves through the same
+        // generator, so it still follows the accounts, and it now composes with
+        // the account dropdown rather than resetting it.
 
         // Order is alphabetical here because childKeys() is genuinely all the
         // INI knows. The user reorders once and it sticks from then on.
@@ -585,6 +579,18 @@ void Config::loadSavedQueries(const QString &configPath, QSettings &settings)
             continue;
         }
 
+        // A stored entry naming a generator now duplicates a BUILT-IN filter of
+        // the same name, since item 93 ships all four rather than storing them.
+        // 0.19.0 migrated the hardcoded Sent button into exactly such an entry,
+        // so every existing install has one.
+        //
+        // Unpinned, never dropped: the row would otherwise carry two Sent
+        // buttons, one the user's to edit and one not. Deleting it would be
+        // data loss on a file whose readers are supposed to preserve what they
+        // do not own, and an unpin is reversible from the UI.
+        if (query.isGenerated() && isKnownGenerator(query.generated))
+            query.pinned = false;
+
         for (auto it = object.begin(); it != object.end(); ++it) {
             static const QStringList known = {
                 QStringLiteral("name"), QStringLiteral("query"),