clarify: a parked question belongs to the conversation that was asked (V-466)

The clarify store had one key for the whole daemon, so a question asked in
the web chat and never answered captured the next three utterances from any
source — telegram, or the mic — and answered them against a request the
speaker never made.

The reach now supplies a conversation id on the IPC Chat call, and the
daemon carries it on the context the way it already carries the correlation
id, so the six clarify call sites read it instead of a constant. The mic has
no id of its own and keeps the key it had, so voice behaves exactly as
before. mavweb has no per-browser session, so every tab is one conversation:
right for a single-owner box, and still distinct from telegram and the mic.

Dialogue sessions stay global on purpose — they are what she remembers about
him, not what she is waiting for from one channel.

cmd/mavend/tick.go

@@ -986,7 +986,7 @@ type daemonAPI struct {
 	getTrace         func() *loop.TickTrace
 	getMorningStatus func(ctx context.Context) []ipc.MorningRoutineStatus
 	getDayPlan       func(ctx context.Context) ipc.DayPlan
-	chatFn           func(ctx context.Context, text string) string
+	chatFn           func(ctx context.Context, conversation, text string) string
 	getMCPServers    func() []ipc.MCPServerStatus
 	getEvents        func(n int) []ipc.IntakeEvent
 }
@@ -1002,11 +1002,11 @@ func (d *daemonAPI) RecentEvents(ctx context.Context, n int) ([]ipc.IntakeEvent,
 	return d.getEvents(n), nil
 }
 
-func (d *daemonAPI) Chat(ctx context.Context, text string) (string, error) {
+func (d *daemonAPI) Chat(ctx context.Context, conversation, text string) (string, error) {
 	if d.chatFn == nil {
 		return "", errors.New("mavend: chat not available")
 	}
-	return d.chatFn(ctx, text), nil
+	return d.chatFn(ctx, conversation, text), nil
 }
 
 // MCPServers — the configured MCP servers and their health (Vikunja #251).