feat: load the contact store once and feed both consumers

MainWindow reads contactsDir() once while building its UI, holds the
result in m_contacts, and hands it to the query bar's completer right
after that is constructed and to every ComposeWindow as it opens. An
empty contactsDir() skips the call, so a machine with no address book
pays nothing and warns about nothing.

The directory is not watched: a restart picks up a vdirsyncer update,
and a QFileSystemWatcher would be a live-index feature nobody asked for.

No action is added, so none of the five places in "Adding an action is
FIVE places" applies: there is no name in KeyMap::knownActions(), no
default binding, no icon-table entry and no menu entry to add.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/mainwindow.h b/src/mainwindow.h
index c3395c9..4fb19e4 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -48,6 +48,10 @@
 // asserted through it without reaching into the delegate.
 #include "businesssenders.h"
 
+// Held by value, like the business-senders list above: the parsed contact list
+// is a member, so its size must be known here.
+#include "contactstore.h"
+
 class QAction;
 class QLineEdit;
 class QMenu;
@@ -1836,6 +1840,16 @@ private:
     /// completer does not yet offer, without a round trip.
     QStringList m_knownTags;
 
+    /// The address book, loaded ONCE when the window is built and handed to
+    /// both consumers: the query-bar completer and every composer.
+    ///
+    /// Held here so the list is read from disk a single time per session. A
+    /// vdirsyncer directory can change while the application runs, but a
+    /// QFileSystemWatcher would be speculative: a restart picks up the new
+    /// file, and the store is 117 files of two fields, not a live index.
+    /// Empty when contactsDir() is unset, which is the feature being off.
+    QList<Contact> m_contacts;
+
     quint64 m_generation = 0;
 
     /// True once the running query has reported its total, so the model holds