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/mavweb/handlers_test.go

@@ -77,7 +77,7 @@ func (f *fakeCore) MCPServers(context.Context) ([]ipc.MCPServerStatus, error) {
 	return f.mcpServers, f.mcpErr
 }
 
-func (f *fakeCore) Chat(_ context.Context, text string) (string, error) {
+func (f *fakeCore) Chat(_ context.Context, _, text string) (string, error) {
 	f.chatText = text
 	if f.chatErr != nil {
 		return "", f.chatErr

cmd/mavweb/main.go

@@ -1678,7 +1678,13 @@ func handleChatAPI(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI, ses
 		http.Redirect(w, r, "/chat", http.StatusSeeOther)
 		return
 	}
-	reply, err := core.Chat(r.Context(), text)
+	// One conversation id for the whole web chat, and a different one from
+	// telegram or the mic. A parked question belongs to the reach that was
+	// asked; before this, a clarify nobody answered on the web ate the next
+	// utterance spoken at the mic (Vikunja #466). This server has no
+	// per-browser session, so every browser tab is the same conversation —
+	// which is right for a single-owner box.
+	reply, err := core.Chat(r.Context(), "web", text)
 	if err != nil {
 		log.Printf("chat api: %v", err)
 		http.Redirect(w, r, "/chat", http.StatusSeeOther)