feat: count a card's messages, not its repliesthread-row-identity

The expander pill read "N replies" while the row stood for the
conversation: a thread of one message and four replies said "4 replies"
over rows that listed all five messages. The user's model is messages, so
it now reads "5 messages". A thread of one still shows nothing: its row is
the message, the pill is the expander, and there is nothing to open.

ReplyCountRole becomes MessageCountRole and CardLayout::Input::replyCount
becomes messageCount, so the names stop lying about what they carry. The
label is now translated under a CardLayout context, with Italian
"messaggio"/"messaggi" shipped; %n's untranslated fallback on this Qt does
not pluralise, so the two forms are separate entries. The card's densest
geometry test needs 460px rather than 400 now that the pill is one
character wider.

1 files changed, 6 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 56d98e4..4bdc536 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -115,6 +115,12 @@ point at which they are stable.
   removes the row at once while an automatic one waits until you move on.
   Reading the last unread message of a long conversation is the one case that
   still waits for the next query or sync.
+- **A conversation's card counts its MESSAGES, not its replies.** The pill
+  that opens the thread read "N replies" against the total the row actually
+  lists: a thread of one message and four replies said "4 replies" over rows
+  for all five messages. It now reads "5 messages", which is what the
+  conversation is. A thread of one message still shows no count at all, since
+  there is nothing for the pill to open.
 - **Delete and Restore appear only where they apply.** Delete is hidden on
   mail already in the trash, where it reported success and did nothing, and
   Restore is hidden on mail that was never deleted.