Say each notification in plain words the operator reads at a glance

The desktop popups were walls of plan ids, commits, keys and verb syntax in UTC.
The messenger now shows the condition's headline, explanation and resolved line,
since when in the operator's time zone, and a clearance in one line (hq ADR 0253).

modules/messenger/cmd/messenger/main.go

@@ -25,6 +25,22 @@ func logf(format string, a ...any) { fmt.Fprintf(os.Stderr, format+"\n", a...) }
 type Settings struct {
 	TelegramChatID  string   `json:"telegram-chat-id"`
 	DesktopMachines []string `json:"desktop-machines"`
+	// TimeZone is the operator's, an IANA name such as Europe/Brussels: every time a message says is said
+	// in it. Empty is this machine's own zone.
+	TimeZone string `json:"time-zone"`
+}
+
+// zoneOf is the location a time-zone setting names, or this machine's own when it names none or one
+// that does not exist (said, never guessed silently).
+func zoneOf(name string) (*time.Location, error) {
+	if name == "" {
+		return time.Local, nil
+	}
+	loc, err := time.LoadLocation(name)
+	if err != nil {
+		return time.Local, fmt.Errorf("the time-zone %q is not one this machine knows; times are said in its own zone", name)
+	}
+	return loc, nil
 }
 
 func readSettings(path string) (Settings, error) {
@@ -47,6 +63,9 @@ func readSettings(path string) (Settings, error) {
 	case float64:
 		s.TelegramChatID = fmt.Sprintf("%.0f", v)
 	}
+	if tz, ok := loose["time-zone"].(string); ok {
+		s.TimeZone = strings.TrimSpace(tz)
+	}
 	if list, ok := loose["desktop-machines"].([]any); ok {
 		for _, m := range list {
 			if name, ok := m.(string); ok && strings.TrimSpace(name) != "" {
@@ -128,7 +147,7 @@ func (l *listening) get() string  { l.mu.Lock(); defer l.mu.Unlock(); return l.n
 func main() {
 	settingsFile := os.Getenv("MESH_MESSENGER_SETTINGS")
 	var said sync.Mutex
-	lastSaid := ""
+	lastSaid, zoneSaid := "", ""
 	settings := func() Settings {
 		s, err := readSettings(settingsFile)
 		said.Lock()
@@ -153,7 +172,20 @@ func main() {
 		},
 		Store: stateStore{},
 		Logf:  logf,
-		Emit:  func(event string, body any) error { return stdio.Emit(event, body) },
+		Zone: func() *time.Location {
+			loc, err := zoneOf(settings().TimeZone)
+			said.Lock()
+			defer said.Unlock()
+			if err != nil && err.Error() != zoneSaid {
+				logf("[messenger] %v", err)
+			}
+			zoneSaid = ""
+			if err != nil {
+				zoneSaid = err.Error()
+			}
+			return loc
+		},
+		Emit: func(event string, body any) error { return stdio.Emit(event, body) },
 	}
 	h.init()
 	l := &listening{now: "not yet: starting"}
@@ -286,7 +318,8 @@ func tools(h *Holder, l *listening) []stdio.Tool {
 			Run:   func(a map[string]any) (any, error) { return h.History(limitArg(a, 50)), nil }},
 		{Name: "operator-channel.notify",
 			Description: "Tell the operator something, as a module that uses the seat: a key (the same key is the same " +
-				"message), urgent or warning, one line in the mesh's words, and what it is about. clear says it is over. " +
+				"message), urgent or warning, one line in the mesh's words, and what it is about; and best, in plain " +
+				"words, a headline, an explanation and the line said when it is over. clear says it is over. " +
 				"Roles and words only: an address, a path or a secret is refused. Deduplicated, capped and routed " +
 				"like the controller's conditions.",
 			Input: map[string]any{
@@ -294,11 +327,16 @@ func tools(h *Holder, l *listening) []stdio.Tool {
 				"severity": map[string]any{"type": "string", "enum": []string{Urgent, Warning}},
 				"summary":  str("one line in the mesh's words"),
 				"subject":  str("what it is about: a machine's role, a module, a plan"),
+				"headline": str("a few plain words the operator reads as the title, e.g. backup failed on ace: no ids, keys or commands"),
+				"explanation": str("one or two plain sentences: what happened, what it means for the operator, and whether " +
+					"they need to act"),
+				"resolved": str("the one short line said when it is over, e.g. backups run again on ace"),
 				"clear":    map[string]any{"type": "boolean", "description": "it is over: the message is edited to say so"},
 			},
 			Run: func(a map[string]any) (any, error) {
 				clear, _ := a["clear"].(bool)
-				return h.Notify(strArg(a, "key"), strArg(a, "severity"), strArg(a, "summary"), strArg(a, "subject"), clear)
+				return h.Notify(strArg(a, "key"), strArg(a, "severity"), strArg(a, "summary"), strArg(a, "subject"), clear,
+					strArg(a, "headline"), strArg(a, "explanation"), strArg(a, "resolved"))
 			}},
 		{Name: "messenger_status",
 			Description: "Whether the operator can be reached, and why not: each channel — can it send, what it lacks " +