v0.256.0: the box sends its own sentence in the household's language (R-558 Part B)

MinAgent: 0.131.0 (unchanged). Needs hub v0.118.0+, which shipped first and
tolerates a box that sends none of this - every box in the fleet is that box
until this release reaches it.

The hub writes a household's e-mails in their language now, but about a third
of those mails carry a sentence the BOX composed, naming a drive, an app or a
number. The hub cannot translate one. So the box sends it twice.

- message_customer on POST /api/v1/event, omitempty. A HUNGARIAN household
  sends nothing extra at all, so its payload stays byte-for-byte what every box
  sends today and the hub's fallback path keeps being the one production
  exercises rather than a branch nobody takes.
- 19 producers render both sentences from ONE bundle key. `message` stays
  Hungarian always: it is what the operator is mailed and what the hub logs.
- customer.language bootstraps a new box - stored choice, then config, then
  Hungarian. The config value is NEVER written into settings.json: that would
  record a choice the household never made.

The Hungarian did not move, measured twice: the wire golden from the slice-2
base commit, and the Go parity gate over all 19 new keys.

Three guards had to learn the change and one caught me: the test seam now
carries the new field; the R-329 severity register reported two dynamic sites
as no longer existing the moment they moved off PushEvent (the walk now checks
36 severity literals, up from 20); and TestConfigLanguageIsWiredInMain reads
main.go, because cmd/ is gitignored and ripgrep does not.

A mistake, named: the first pass dropped displayName from three producers,
which would have mailed customers "Alkalmazás telepítve: %!s(MISSING)". Caught
reading the diff; now pinned by a test that refuses %!/MISSING/%s/%d in either
language.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/notify/disk_health_test.go

@@ -38,7 +38,7 @@ func hubSeverityNotifies(sev string) bool {
 func TestNotifyDiskHealthDegraded_SeverityRoutes(t *testing.T) {
 	n := &Notifier{}
 	var gotSev string
-	n.pushFn = func(eventType, severity, message string, details interface{}) { gotSev = severity }
+	n.pushFn = func(eventType, severity, message, _ string, details interface{}) { gotSev = severity }
 
 	n.NotifyDiskHealthDegraded(DiskAlert{Label: "sdb", Kind: DiskAlertWarn,
 		Attributes: []string{"függőben lévő szektorok"}})
@@ -70,7 +70,7 @@ func TestNotifyDiskHealthDegraded_WarnShape(t *testing.T) {
 	n := &Notifier{}
 	var gotType, gotMsg string
 	var gotDetails interface{}
-	n.pushFn = func(eventType, severity, message string, details interface{}) {
+	n.pushFn = func(eventType, severity, message, _ string, details interface{}) {
 		gotType, gotMsg, gotDetails = eventType, message, details
 	}
 
@@ -100,7 +100,9 @@ func TestNotifyDiskHealthDegraded_FailShapes(t *testing.T) {
 	n := &Notifier{}
 	var gotMsg string
 	var gotDetails interface{}
-	n.pushFn = func(eventType, severity, message string, details interface{}) { gotMsg, gotDetails = message, details }
+	n.pushFn = func(eventType, severity, message, _ string, details interface{}) {
+		gotMsg, gotDetails = message, details
+	}
 
 	cases := []struct {
 		name        string
@@ -154,7 +156,7 @@ func TestNotifyDiskHealthDegraded_FailShapes(t *testing.T) {
 func TestNotifyDiskHealthDegraded_CopyDiscipline(t *testing.T) {
 	n := &Notifier{}
 	var gotMsg string
-	n.pushFn = func(eventType, severity, message string, details interface{}) { gotMsg = message }
+	n.pushFn = func(eventType, severity, message, _ string, details interface{}) { gotMsg = message }
 	for _, k := range []DiskAlertKind{DiskAlertWarn, DiskAlertFailSelfReported, DiskAlertFailSectors, DiskAlertFailTemperature, DiskAlertFailWorsened} {
 		n.NotifyDiskHealthDegraded(DiskAlert{Label: "TESTDISK", Kind: k, Sectors: 8, TemperatureC: 61})
 		if !strings.Contains(gotMsg, "TESTDISK") {