reminders: store what she says, show it in his clock (V-469)

Two of the four defects on the task.

The stored payload was the whole utterance, so /reminders and the agenda
recited "напомни завтра в 9 утра выпить таблетки" where the reminder is
"выпить таблетки". The marker is an instruction that was already carried out
and the hour is already a column, so reminderBody strips both, and falls back
to the unstripped body whenever stripping would leave nothing — a reminder
that fires and says nothing is worse than a wordy one.

The page rendered the raw {"text":...} envelope and the UTC instant. Both are
now done in mavweb: reminderRows unwraps the payload and formats through
Local(). The unwrap is a copy of store.ReminderText rather than a call to it,
because mavweb builds without CGO and internal/store carries the sqlite
driver — the ipc DTOs are decoupled from the store on purpose.

TestClarifySubjectAnswerFillsRatherThanClobbers asserted the hour survived as
a word in the payload. It now asserts the fire time, which is where the hour
lives.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavweb/reminders_test.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/kami/maven/internal/ipc"
+)
+
+// The page showed the storage envelope and the UTC instant (Vikunja #469).
+func TestReminderRowsUnwrapAndLocalise(t *testing.T) {
+	fire := time.Date(2026, 8, 4, 18, 30, 0, 0, time.UTC)
+	rows := reminderRows([]ipc.Reminder{{
+		CreatedTs: fire.Add(-time.Hour),
+		FireTs:    fire,
+		Status:    "pending",
+		Payload:   `{"text":"выпить таблетки"}`,
+	}})
+	if len(rows) != 1 {
+		t.Fatalf("rows = %d, want 1", len(rows))
+	}
+	if rows[0].Text != "выпить таблетки" {
+		t.Errorf("Text = %q, want the words without the envelope", rows[0].Text)
+	}
+	if want := fire.Local().Format("02 Jan 15:04"); rows[0].Fires != want {
+		t.Errorf("Fires = %q, want %q", rows[0].Fires, want)
+	}
+	if strings.Contains(rows[0].Text, "{") {
+		t.Errorf("Text still carries JSON: %q", rows[0].Text)
+	}
+}
+
+// A payload that is not the envelope is his own words, so it is shown as it is.
+func TestReminderTextKeepsPlainPayload(t *testing.T) {
+	for _, tc := range []struct{ in, want string }{
+		{`{"text":"позвонить маме"}`, "позвонить маме"},
+		{"  полить цветы  ", "полить цветы"},
+		{`{"body":"nope"}`, `{"body":"nope"}`},
+		{"", ""},
+	} {
+		if got := reminderText(tc.in); got != tc.want {
+			t.Errorf("reminderText(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}