feat(ui): friendly RPC errors + pause-on-hover/ellipsis toasts

Two of the systemic error-surfacing foundations from the UX audit:

- util::friendlyRpcError() maps the common raw daemon/JSON-RPC errors
  (warming up / -28, locked / -13, method-not-found / -32601, insufficient
  funds, unreachable node) to short translated guidance with a next step,
  falling back to the trimmed raw text. Wired into the send (money) path: the
  toast shows the friendly cause, the overlay keeps the raw text below it for
  diagnostics. The helper is reusable for the remaining raw-error sites.
- Toasts now pause their auto-dismiss while hovered and ellipsize over-long
  text with the full message in a hover tooltip, instead of hard-clipping it
  mid-word (durations were already lengthened earlier).

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

src/ui/notifications.cpp

@@ -14,6 +14,11 @@ namespace ui {
 
 void Notifications::render()
 {
+    // Pause-on-hover: while the pointer rests on the toast, keep it alive so a long error message can
+    // actually be read (errors/warnings already last longer, but hovering holds any of them open).
+    if (toast_hovered_ && !notifications_.empty())
+        notifications_.back().created_at = std::chrono::steady_clock::now();
+
     // Remove every expired notification; the newest remaining one is then both the last and a live one.
     pruneExpired(notifications_, std::chrono::steady_clock::now());
 
@@ -146,13 +151,35 @@ void Notifications::render()
         cursorX += iconW + iconGap;
     }
 
-    // Message text (clipped to pill bounds)
+    // Message text — ellipsized to fit the (viewport-clamped) pill rather than hard-clipped mid-word,
+    // with the full text shown in a tooltip on hover.
+    bool clipped = false;
     if (textFont) {
         ImU32 textCol = ImGui::ColorConvertFloat4ToU32(text_color);
+        const float availTextW = (pMax.x - pillPadX) - cursorX;
+        std::string shown = notif.message;
+        if (availTextW > 0.0f &&
+            textFont->CalcTextSizeA(textFont->LegacySize, FLT_MAX, 0.0f, shown.c_str()).x > availTextW) {
+            clipped = true;
+            const std::string ell = "\xE2\x80\xA6";   // "…"
+            while (!shown.empty() &&
+                   textFont->CalcTextSizeA(textFont->LegacySize, FLT_MAX, 0.0f,
+                                           (shown + ell).c_str()).x > availTextW) {
+                shown.pop_back();
+                while (!shown.empty() && (static_cast<unsigned char>(shown.back()) & 0xC0) == 0x80)
+                    shown.pop_back();   // drop any trailing UTF-8 continuation bytes
+            }
+            shown += ell;
+        }
         dl->PushClipRect(ImVec2(cursorX, pillY), ImVec2(pMax.x - pillPadX, pMax.y), true);
-        dl->AddText(textFont, textFont->LegacySize, ImVec2(cursorX, contentY), textCol, notif.message.c_str());
+        dl->AddText(textFont, textFont->LegacySize, ImVec2(cursorX, contentY), textCol, shown.c_str());
         dl->PopClipRect();
     }
+
+    // Hover: pause the auto-dismiss (handled next frame) and reveal the full message if it was clipped.
+    toast_hovered_ = ImGui::IsMouseHoveringRect(pMin, pMax);
+    if (toast_hovered_ && clipped)
+        ImGui::SetTooltip("%s", notif.message.c_str());
 }
 
 } // namespace ui

src/ui/notifications.h

@@ -192,6 +192,7 @@ private:
 
     std::deque<Notification> notifications_;
     size_t max_notifications_ = 5;
+    bool toast_hovered_ = false;   // pointer was over the toast last frame → pause its auto-dismiss
     std::chrono::steady_clock::time_point last_drawn_{};
     std::function<void(const std::string&, bool)> console_callback_;
 

src/ui/windows/send_tab.cpp

@@ -927,10 +927,14 @@ void RenderSendConfirmPopup(App* app) {
                             s_memo[0] = '\0';
                             s_send_max = false;
                         } else {
-                            s_tx_status = std::string(TR("send_error_prefix")) + result;
+                            // Show a friendly cause in the toast; keep the raw backend text below it in
+                            // the overlay (copyable) so the detail isn't lost for diagnostics.
+                            const std::string friendly = util::friendlyRpcError(result);
+                            s_tx_status = std::string(TR("send_error_prefix")) + friendly +
+                                          (friendly != result ? "\n\n" + result : std::string());
                             s_result_txid.clear();
                             s_status_success = false;
-                            Notifications::instance().error(std::string(TR("send_tx_failed")) + result);
+                            Notifications::instance().error(std::string(TR("send_tx_failed")) + friendly);
                         }
                     }
                 );