Cancel a reminder by voice, and honour a refusal (V-719)

reminder_cancel.go is a stateful pre-route resolver ahead of a parked
clarification and the statistical cascade. It accepts only an addressed
command-position imperative plus the reminder or alarm noun, so questions,
reported speech, past-tense reports and prohibitions establish no mutation
authority. Subject terms keep negation and quantity, and a parsed time
passes the same resolved-hour gate as capture.

One match cancels through the typed IPC method. Several are stored as
session candidates in the spoken order, capped at five, and only a whole
affirmative ordinal consumes that list: re-querying on the follow-up would
let a state change move the ordinal underneath him. No match, an unread
time, a spent ordinal and an ambiguous delivery result are all explicit
no-ops.

command_prohibition.go is the first mutation boundary in a turn. A direct
prohibition clears the three confirmation slots under their shared mutex,
so a later bare "да" cannot revive authority he has just revoked. A parked
clarify question is not authority and survives, suspended and repeated.
refusesCommand is the same belt at the executor entry points, checked
against the original utterance so a model rewriting Slots.Text cannot get
around it.

The rung is named in preRouteLadder, so /trace records whether it won or
declined on every surface.

--no-verify: master is the working branch this session by the owner's call.

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

cmd/mavend/self.go

@@ -6,6 +6,7 @@ import (
 	"regexp"
 
 	"github.com/kami/maven/internal/phraser"
+	"github.com/kami/maven/internal/router"
 )
 
 // A question about her — "что ты умеешь", "кто ты" — used to have no answer at
@@ -98,6 +99,16 @@ func selfFloor(utterance string) bool {
 // asked — "что ты умеешь" and "кто ты" want different halves of it — and falls
 // back to the text itself, which is already readable, if the model is down.
 func (h *reactiveHandler) querySelf(ctx context.Context, t *queryTurn) (string, bool) {
+	// Product help is self knowledge too (Vikunja V-720), but unlike the prose description it
+	// must be exact: these examples name the grammar Maven actually accepts.
+	// Answer them before topic scoring so a phrasing such as "как отменить
+	// задачу" cannot leak to SearXNG as generic third-party instructions.
+	switch router.LocalHelpTopic(t.dec.Utterance) {
+	case router.HelpReminderCancel:
+		return "Скажи, например: «отмени напоминание про молоко». Если совпадений несколько, я попрошу выбрать одно.", true
+	case router.HelpTaskDrop:
+		return "Скажи, например: «убери из задач настроить бэкапы». Я уберу задачу из активного списка, не отмечая её выполненной.", true
+	}
 	if !h.turnIsAbout(ctx, t, topicSelf, selfFloor) {
 		return "", false
 	}