fix(drafts): index a saved draft so it appears without a sync

Autosave writes the draft to the Maildir drafts folder and stops, while
the Drafts view is a notmuch path: query, so a freshly saved draft was
invisible until notmuch new ran. saveDraftNow() now emits draftSaved, and
MainWindow connects it to a new NotmuchWorker::indexDraftFile() that
indexes the one file the way moveMessages() does, with the previous
revision removed so a rewrite leaves no ghost.

The send path unlinks a draft that was indexed while being composed, so
draftRemoved -> removeIndexedFile() drops its entry too.

Measured: notmuch_database_index_file assigns NO tags (unlike notmuch
new, which adds draft inbox unread), so no tag-stripping is needed and the
draft cannot leak into a tag:inbox view.

Item 158.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/composewindow.h b/src/composewindow.h
index 918d4e3..caff011 100644
--- a/src/composewindow.h
+++ b/src/composewindow.h
@@ -168,6 +168,17 @@ signals:
     /// pointer before WA_DeleteOnClose destroys the window.
     void closed(ComposeWindow *window);
 
+    /// A draft was written to disk, so the window's owner can index it and it
+    /// appears in the Drafts view without a full sync (item 158).
+    ///
+    /// \p path is the file just written, absolute. \p previousPath is the file
+    /// the write replaced, empty on the first save of a new draft.
+    void draftSaved(const QString &path, const QString &previousPath);
+
+    /// A draft file was unlinked (sent), so its index entry must go too.
+    /// \p path is the file that was removed, absolute.
+    void draftRemoved(const QString &path);
+
 protected:
     /// The one place the registry is told, whichever route closes the window.
     void closeEvent(QCloseEvent *event) override;