feat(chat): Accept/Block card for unsolicited contact requests

An unsolicited first message from a stranger (an incoming ContactRequest, with
nothing sent by us and the peer not in contacts) now shows an Accept / Block
card above the thread instead of looking like a normal conversation. Accept adds
the peer to the address book (which clears the request state); Block deletes and
blocks the conversation (reversible from the Blocked manager). ConvSummary gains
a derived pendingRequest flag. (The list-row "Request" pill and a header Block
button were left out to avoid the fragile hand-drawn header-toolbar geometry.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/chat_tab.cpp

@@ -537,6 +537,7 @@ struct ConvSummary {
     std::int64_t lastTs = 0;
     int count = 0;
     bool hidden = false;     // shown only while "Show hidden" is on
+    bool pendingRequest = false;  // unsolicited incoming contact request from a stranger: awaiting Accept/Block
 };
 
 // Per-frame memoization of the conversation-list build and the open-thread message list (both otherwise
@@ -808,9 +809,11 @@ void RenderChatTab(App* app)
             c.cid = cid;
             c.hidden = hidden;
             c.count = static_cast<int>(messages.size());
+            bool sentAny = false;
             for (const auto& m : messages) {  // pin to the EARLIEST (establishing) peer z-addr / key (B2 — the
                 if (c.peerZaddr.empty() && !m.peer_zaddr.empty()) c.peerZaddr = m.peer_zaddr;   // memo header rides
                 if (c.peerPubKey.empty() && !m.peer_public_key_hex.empty()) c.peerPubKey = m.peer_public_key_hex; // outside the AEAD)
+                if (m.direction == chat::ChatDirection::Outgoing) sentAny = true;
             }
             const auto& last = messages.back();
             c.lastBody = last.body;
@@ -818,6 +821,12 @@ void RenderChatTab(App* app)
             const int idx = c.peerZaddr.empty() ? -1 : book.findByAddress(c.peerZaddr);
             c.peerName = (idx >= 0) ? book.entries()[idx].label
                                     : shorten(!c.peerZaddr.empty() ? c.peerZaddr : cid);
+            // Unsolicited: first message is an incoming contact request, we've never replied, and the peer
+            // isn't a saved contact → show an Accept/Block card instead of treating it as a normal chat.
+            const auto& first = messages.front();
+            c.pendingRequest = (idx < 0) && !sentAny && !c.peerZaddr.empty() &&
+                               first.direction == chat::ChatDirection::Incoming &&
+                               first.kind == chat::ChatMessageKind::ContactRequest;
             s_convs.push_back(std::move(c));
         }
         std::sort(s_convs.begin(), s_convs.end(),
@@ -1340,6 +1349,42 @@ void RenderChatTab(App* app)
             ImGui::SetCursorScreenPos(ImVec2(hp.x, hp.y + rowH + 4.0f * hdpi));
             ImGui::Separator();
 
+            // Stranger contact-request card: Accept (add to contacts) or Block (delete + block). Normal
+            // ImGui flow, so ##ChatMessages below (sized from the remaining content height) shrinks to fit.
+            if (sel->pendingRequest) {
+                ImGui::Dummy(ImVec2(0, Layout::spacingSm()));
+                ImGui::PushStyleColor(ImGuiCol_Text, ImGui::ColorConvertU32ToFloat4(material::Warning()));
+                ImGui::TextUnformatted(TR("chat_request_title"));
+                ImGui::PopStyleColor();
+                ImGui::PushTextWrapPos(0.0f);
+                ImGui::TextWrapped("%s", TR("chat_request_body"));
+                ImGui::PopTextWrapPos();
+                ImGui::Dummy(ImVec2(0, Layout::spacingXs()));
+                if (ImGui::SmallButton(TR("chat_request_accept"))) {
+                    data::AddressBookEntry e;
+                    e.address = sel->peerZaddr;
+                    e.label = sel->peerName;
+                    book.addEntry(e);   // book.revision() bumps → the request flag clears on the next rebuild
+                    Notifications::instance().info(TR("chat_request_accepted"));
+                }
+                ImGui::SameLine();
+                if (ImGui::SmallButton(TR("chat_request_block"))) {
+                    const std::string cid = sel->cid, nm = sel->peerName;   // copy before deleteConversation
+                    if (app->chatService().deleteConversation(cid, /*block=*/true)) {
+                        if (app->settings()) {
+                            app->settings()->setChatBlocked(cid, nm, true);
+                            app->settings()->setChatHidden(cid, false);
+                            app->settings()->save();
+                        }
+                        if (s_selected_cid == cid) s_selected_cid.clear();
+                        Notifications::instance().info(TR("chat_blocked_toast"));
+                    } else {
+                        Notifications::instance().error(TR("chat_delete_failed"));
+                    }
+                }
+                ImGui::Separator();
+            }
+
             const float dp = Layout::dpiScale();
             // Small message-list inset (the ##ChatThread WindowPadding above already holds content off
             // the glass edge; keep a little here so bubbles don't hug the scrollbar).

src/util/i18n.cpp

@@ -232,6 +232,11 @@ void I18n::loadBuiltinEnglish()
         strings_["chat_empty_hint"] = "No conversations yet. Messages you receive will appear here.";
         strings_["chat_you"] = "You";
         strings_["chat_contact_request"] = "contact request";
+        strings_["chat_request_title"] = "New contact request";
+        strings_["chat_request_body"] = "This person isn't in your contacts. Accept to add them, or block to delete this conversation and ignore them.";
+        strings_["chat_request_accept"] = "Accept";
+        strings_["chat_request_block"] = "Block";
+        strings_["chat_request_accepted"] = "Contact added.";
         strings_["chat_send_failed"] = "not sent";
         strings_["chat_status_sending"] = "Sending… waiting for your wallet to broadcast it";
         strings_["chat_status_sent"] = "Sent to the network — it arrives after it confirms (about a minute)";