Bound shutdown hooks by their stop context (closes #102)

fx hands OnStop a context carrying the application's stop timeout,
and the delivery engine, the retention reaper, and the archive
sweeper all discarded it and called wg.Wait() bare. A worker wedged
inside a delivery target that never returns, or a sweep blocked on a
locked SQLite database, hung the process forever instead of letting
it exit when the timeout expired.

All three now wait through internal/lifecycle.WaitForShutdown, which
selects the drained WaitGroup against the stop context and, on
timeout, logs at error naming the component and returns an error
rather than reporting a clean stop.

Engine.stop also gains the cancel != nil guard its two mirrored
components already had.

internal/delivery/archive_sweeper_test.go

@@ -14,7 +14,6 @@ import (
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"go.uber.org/fx"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 	"gorm.io/gorm/clause"
@@ -226,17 +225,6 @@ func countArchivedRows(path string) (int64, error) {
 	return count, nil
 }
 
-// captureLifecycle is a minimal fx.Lifecycle that records the
-// hooks a component registers, so a test can invoke the real
-// OnStart/OnStop functions with a context of its choosing.
-type captureLifecycle struct {
-	hooks []fx.Hook
-}
-
-func (l *captureLifecycle) Append(h fx.Hook) {
-	l.hooks = append(l.hooks, h)
-}
-
 // TestArchiveSweeper_LoopOutlivesStartHookContext is the
 // regression test for a sweeper that never swept. fx calls
 // OnStart with a context carrying the application's start
@@ -270,7 +258,7 @@ func TestArchiveSweeper_LoopOutlivesStartHookContext(
 
 	// Drive the genuine fx hooks the application registers,
 	// rather than a test-only entry point.
-	lc := &captureLifecycle{}
+	lc := &recordingLifecycle{}
 	env.sweeper.ExportRegisterHooks(lc)
 	require.Len(t, lc.hooks, 1)
 
@@ -924,7 +912,36 @@ func TestArchiveSweeper_StopsCleanly(t *testing.T) {
 	env.sweeper.ExportSetInterval(time.Millisecond)
 	env.sweeper.ExportStart()
 
-	// stop blocks on the loop's WaitGroup, so returning at all
-	// proves the loop observed the cancellation and exited.
-	env.sweeper.ExportStop()
+	// stop blocks on the loop's WaitGroup, so returning without
+	// error proves the loop observed the cancellation and exited
+	// well inside the stop context.
+	require.NoError(
+		t, env.sweeper.ExportStop(context.Background()),
+	)
+}
+
+// TestArchiveSweeper_StopHookHonoursStopTimeout is the sweeper's
+// half of the same shutdown defect the engine and the retention
+// reaper carried: an OnStop that discards its context and waits
+// on the WaitGroup bare hangs the process forever on a prune
+// wedged inside a locked archive.
+func TestArchiveSweeper_StopHookHonoursStopTimeout(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	env := setupSweeperTest(t)
+
+	lc := &recordingLifecycle{}
+	env.sweeper.ExportRegisterHooks(lc)
+	require.Len(t, lc.hooks, 1)
+	require.NoError(t, lc.hooks[0].OnStart(context.Background()))
+
+	release := make(chan struct{})
+
+	t.Cleanup(func() { close(release) })
+
+	env.sweeper.ExportWedgeLoop(release)
+
+	requireStopHookExpires(t, lc.hooks[0], "archive sweeper")
 }