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, 134 insertions, 0 deletions

diff --git a/assets/hooks/qtmaildirconf.py b/assets/hooks/qtmaildirconf.py
new file mode 100755
index 0000000..e709a28
--- /dev/null
+++ b/assets/hooks/qtmaildirconf.py
@@ -0,0 +1,134 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+"""Reads the account layout out of qtmaildir.conf, for the post-new hook.
+
+Only the sent folders are read, and only so the hook can tell mail the user
+SENT from mail that arrived. Everything else in that file belongs to the
+application.
+
+Stdlib only: this is imported by a notmuch hook that runs on every sync.
+
+The file is written by QSettings rather than by configparser, and the two
+disagree in one place that matters here. QSettings treats `/` in a section
+name as a group separator, so accounts are `[account.<key>]` with a DOT, and
+that key may itself contain dots (`[account.provider.name]`). The account key
+is therefore everything after the FIRST dot, never a split on the last one.
+"""
+
+import configparser
+from pathlib import Path
+
+ACCOUNT_PREFIX = "account."
+
+
+def default_path():
+    """~/.config/qtmaildir/qtmaildir.conf, honouring XDG_CONFIG_HOME.
+
+    Read through the environment rather than hardcoded so a test can point
+    at a throwaway config, which is how the hook's own tests reach it.
+    """
+    import os
+    base = os.environ.get("XDG_CONFIG_HOME") or (Path.home() / ".config")
+    return Path(base) / "qtmaildir" / "qtmaildir.conf"
+
+
+def _accounts(path):
+    """Every `[account.*]` section as a dict, or nothing at all.
+
+    A file that will not parse yields NO accounts rather than raising. The
+    caller is a hook running after `notmuch new` has already indexed the
+    mail: failing the sync over a malformed application config is worse than
+    not protecting sent mail for one cycle, and the hook logs the miss.
+    """
+    parser = configparser.ConfigParser(
+        # QSettings writes `;` comments, and `#` appears inside values (a
+        # colour is `#2f6fa8`), so `#` must NOT introduce a comment.
+        comment_prefixes=(";",),
+        # A value may contain `%` and `$`; neither is an interpolation here.
+        interpolation=None,
+        # `[Gmail]/Posta inviata` is a legal value. Nothing in this file
+        # relies on duplicate keys, but tolerating them beats raising.
+        strict=False)
+    try:
+        # Explicit UTF-8: QSettings writes it, and the C locale would
+        # otherwise decide.
+        with open(path, encoding="utf-8") as handle:
+            parser.read_file(handle)
+    except (OSError, UnicodeDecodeError, configparser.Error):
+        return []
+
+    return [(name[len(ACCOUNT_PREFIX):], parser[name])
+            for name in parser.sections()
+            if name.startswith(ACCOUNT_PREFIX)]
+
+
+# Folders mail does not ARRIVE in: this system put the message there itself.
+#
+# Trash is deliberately absent. qtmaildir's own Delete leaves `inbox` on a
+# trashed message so Restore can put it back where it came from, and stripping
+# it here would fight that.
+NOT_ARRIVALS = ("sent", "drafts")
+
+
+def sent_folders(path=None):
+    """Every folder mail does not arrive in, relative to the mail root.
+
+    An account contributes nothing unless it names a maildir: a bare `Sent`
+    would match every account's folder of that name at once. Each of the keys
+    in NOT_ARRIVALS is optional on its own, since an account may keep no sent
+    mail or no drafts locally.
+    """
+    if path is None:
+        path = default_path()
+
+    folders = []
+    for _key, section in _accounts(path):
+        maildir = section.get("maildir", "").strip()
+        if not maildir:
+            continue
+        for key in NOT_ARRIVALS:
+            folder = section.get(key, "").strip()
+            if folder:
+                folders.append(f"{maildir}/{folder}")
+    return folders
+
+
+def sent_query(folders):
+    """A notmuch query matching everything inside the given folders.
+
+    Empty for an empty list, and the caller MUST check: an empty query means
+    "match everything" to notmuch, so handing this straight to a tag command
+    would treat the whole corpus as sent mail.
+
+    `path:` is hierarchical, so `<folder>/**` covers `cur/` and `new/` and
+    any nesting a provider invents underneath.
+    """
+    if not folders:
+        return ""
+
+    terms = [f'path:"{_quote(folder)}/**"' for folder in folders]
+    return " or ".join(terms)
+
+
+def _quote(value):
+    """Escape a folder name for a double-quoted notmuch term.
+
+    Backslashes BEFORE quotes: the other order escapes the backslashes just
+    added. Same rule as SearchTerm::quote() in the application, and the same
+    reason.
+    """
+    return value.replace("\\", "\\\\").replace('"', '\\"')