shutdown: close the sockets, or the database never gets sealed

mavend seals its encrypted database in `defer st.Close()` when run() returns.
It had not returned since 2026-07-21. Every restart since then decrypted the
same eleven-day-old ciphertext and rolled back everything written in between:
the Telegram nudge that kept firing was a fact being un-written on each boot.

The goroutine dump named it. main → srv.Close() → ipc.(*Server).Close →
wg.Wait(), waiting on per-connection goroutines parked in readFrame. Close
shut the listener and nothing else, so the idle persistent sockets held by
mavweb, mavpoll, mavcaldav and mavmaild blocked shutdown forever. `docker
compose stop -t 60` spent the whole sixty seconds and then took a SIGKILL.

So: track the accepted conns and close them, in ipc and in voice, which had
the identical defect. Bound all three waits — the two per-server ones and the
worker wait in main — because the seal matters more than any single in-flight
call. A dropped RPC costs one reply; a missed seal costs a session.

The regression test leaves a client connected and idle, which is the case the
old tests avoided by closing the client first.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TrVSBKe3RFDF4fGYKWYQnX

internal/ipc/server.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log"
 	"net"
 	"os"
 	"sync"
@@ -451,6 +452,19 @@ type Server struct {
 	done   chan struct{}
 	accept sync.Mutex // guards wg.Add vs Close's wg.Wait sequence
 
+	// conns — every accepted connection still being served. Close needs these
+	// because closing the listener does nothing to a connection already
+	// accepted: serveConn is parked in readFrame waiting for a peer that may
+	// never say anything again, and the wg.Wait below would block forever.
+	//
+	// This was not theoretical. mavweb, mavpoll, mavcaldav and mavmaild all
+	// hold a long-lived connection open, so on 2026-08-01 mavend deadlocked on
+	// every single shutdown, never returned from run(), and never reached the
+	// `defer st.Close()` that seals the database. The deployed ciphertext was
+	// eleven days stale before anyone noticed.
+	connMu sync.Mutex
+	conns  map[net.Conn]struct{}
+
 	// Check — optional authorization hook. dispatch runs it BEFORE method
 	// dispatch, with the raw params, so the auth layer can make verdicts
 	// that depend on the call's shape (e.g. WriteFact's source). A non-nil
@@ -648,8 +662,10 @@ func (s *Server) Serve() error {
 		s.accept.Lock()
 		s.wg.Add(1)
 		s.accept.Unlock()
+		s.trackConn(c)
 		go func(c net.Conn) {
 			defer s.wg.Done()
+			defer s.untrackConn(c)
 			defer c.Close()
 			s.serveConn(c)
 		}(c)
@@ -1231,18 +1247,88 @@ func (s *Server) Close() error {
 		close(s.done)
 	}
 	err := s.ln.Close()
+	// Closing the listener stops new connections; it does nothing to the ones
+	// already accepted. Close those too, or every serveConn parked in readFrame
+	// waits on a peer that has no reason to hang up and the Wait below never
+	// returns. See the comment on Server.conns.
+	s.closeConns()
 	// Under accept lock: after the listener closes, no new Accept can complete,
 	// so no new wg.Add will be called. The Wait is safe to observe the wg
 	// counter because any in-flight Accept that already got a conn either
 	// already called wg.Add (before releasing the lock) or will see the closed
 	// listener error and not call wg.Add at all.
 	s.accept.Lock()
-	s.wg.Wait()
+	waited := waitTimeout(&s.wg, closeGrace)
 	s.accept.Unlock()
+	if !waited {
+		// Bounded on purpose. A dispatch can be mid-call into the resident
+		// model, which has its own timeout measured in tens of seconds, and the
+		// caller of Close is on its way to sealing the database with whatever
+		// grace the supervisor allows. Abandoning one in-flight RPC is cheap;
+		// missing the seal costs every write since the last clean shutdown.
+		log.Printf("ipc: %d connection(s) still busy after %s, closing anyway", s.liveConns(), closeGrace)
+	}
 	_ = os.Remove(s.path)
 	return err
 }
 
+// closeGrace — how long Close waits for in-flight dispatches to finish before
+// giving up on them. Well inside the ten seconds docker allows by default, so
+// the caller still has time to seal.
+const closeGrace = 3 * time.Second
+
+func (s *Server) trackConn(c net.Conn) {
+	s.connMu.Lock()
+	defer s.connMu.Unlock()
+	if s.conns == nil {
+		s.conns = make(map[net.Conn]struct{})
+	}
+	s.conns[c] = struct{}{}
+}
+
+func (s *Server) untrackConn(c net.Conn) {
+	s.connMu.Lock()
+	defer s.connMu.Unlock()
+	delete(s.conns, c)
+}
+
+func (s *Server) liveConns() int {
+	s.connMu.Lock()
+	defer s.connMu.Unlock()
+	return len(s.conns)
+}
+
+// closeConns closes every live connection, which is what unblocks the reads.
+// The serveConn goroutines see the resulting error and return.
+func (s *Server) closeConns() {
+	s.connMu.Lock()
+	live := make([]net.Conn, 0, len(s.conns))
+	for c := range s.conns {
+		live = append(live, c)
+	}
+	s.connMu.Unlock()
+	for _, c := range live {
+		_ = c.Close()
+	}
+}
+
+// waitTimeout waits on wg for at most d, reporting whether it finished. The
+// abandoned goroutines are still holding a wg count, so nothing may reuse the
+// WaitGroup afterwards — Close is terminal, which is what makes this safe.
+func waitTimeout(wg *sync.WaitGroup, d time.Duration) bool {
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+	select {
+	case <-done:
+		return true
+	case <-time.After(d):
+		return false
+	}
+}
+
 // Path returns the filesystem path of the listening socket.
 func (s *Server) Path() string { return s.path }