Merge branch 'compose-and-send': composing and sending mail

Item 123, built over 2026-08-20 to 2026-08-23 in thirteen tasks against
docs/superpowers/specs/2026-08-20-compose-and-send-design.md.

The application writes mail now. A composer window per message, markdown as
the body, drafts autosaving into the account's Maildir, and sending through a
per-account command on stdin rather than any network protocol of this
program's own. A countdown with an Undo stands between pressing Send and the
command running.

Two things came in alongside it. The notmuch auto-tagging hooks moved here
from the retiring `mailctl` project and learned that mail this application
files itself never arrived, so sent mail and drafts stop appearing in the
inbox. And the v1/v2 language is retired: semver on the user-visible surface
is the rule, and those labels described a split that composing made obsolete.

Hand tested against a fake send command rather than a real one, deliberately:
New, Reply and Forward all produce correct messages, a forwarded attachment
survives intact, and the sent copy is filed. That testing found the two
defects fixed on this branch, and both were invisible to the suite: a composer
orphaned by quitting the main window, and every sent message tagged `inbox`.

Twenty-two defects were found in the plan document's own draft code while
building it, which is why CLAUDE.md says to treat every code block in a plan
as a draft.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/mimeparser.cpp b/src/mimeparser.cpp
index 2782a4a..c1198b8 100644
--- a/src/mimeparser.cpp
+++ b/src/mimeparser.cpp
@@ -412,9 +412,11 @@ ParsedMessage MimeParser::parse(const QString &filePath) const
     out.subject = QString::fromUtf8(
         g_mime_message_get_subject(message) ?: "");
     out.from = headerText(message, "From");
+    out.replyTo = headerText(message, "Reply-To");
     out.to = headerText(message, "To");
     out.cc = headerText(message, "Cc");
     out.date = headerText(message, "Date");
+    out.references = headerText(message, "References");
     out.messageId = QString::fromUtf8(
         g_mime_message_get_message_id(message) ?: "");