fix(ui): overview/mining polish + default-pool cleanup

- balance: inset the address-row favorite (star) button by the card's inner
  padding so it mirrors the left margin instead of hugging the card edge.
- mining: remove pool.dragonx.cc from the built-in default pools (pool.dragonx.is
  is now the sole default); update the pool-registry test accordingly.
- mining: middle-truncate saved pool-URL and payout-address dropdown rows (new
  shared material::TruncateToWidth helper) so a full z-address no longer runs
  under the trailing delete (X) button.
- mining: fix the thread-grid cells overflowing the card at >100% display
  scaling — the reserved Mine-button width used a raw clamp that didn't scale;
  scale it by dp so cols is estimated correctly (no-op at 100%).

Full-node build + test suite green.

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

src/ui/windows/mining_mode_toggle.cpp

@@ -308,11 +308,14 @@ void RenderMiningModeToggle(App* app, const WalletState& state, const MiningInfo
                             pdl->AddRectFilled(rowMin, rowMax, IM_COL32(255, 255, 255, 10));
                         if (rowHov && !inXZone)
                             pdl->AddRectFilled(rowMin, rowMax, StateHover());
-                        // Item text with internal padding
+                        // Item text with internal padding, middle-truncated so a long saved URL
+                        // can't run under the trailing X (delete) button.
                         float textY = rowMin.y + (rowH - rowFontSz) * 0.5f;
+                        float maxTextW = popupInnerW - xZoneW - textPadX * 2.0f;
+                        std::string urlDisp = material::TruncateToWidth(url, rowFont, rowFontSz, maxTextW);
                         pdl->AddText(rowFont, rowFontSz,
                             ImVec2(rowMin.x + textPadX, textY),
-                            isCurrent ? Primary() : OnSurface(), url.c_str());
+                            isCurrent ? Primary() : OnSurface(), urlDisp.c_str());
                         // X button — flush with right edge, icon centered
                         {
                             ImVec2 xMin(rowMax.x - xZoneW, rowMin.y);
@@ -467,11 +470,14 @@ void RenderMiningModeToggle(App* app, const WalletState& state, const MiningInfo
                             pdl->AddRectFilled(rowMin, rowMax, IM_COL32(255, 255, 255, 10));
                         if (rowHov && !inXZone)
                             pdl->AddRectFilled(rowMin, rowMax, StateHover());
-                        // Full address text with internal padding
+                        // Address text with internal padding, middle-truncated so a full z-address
+                        // (~78 chars) can't run under the trailing X (delete) button.
                         float textY = rowMin.y + (wRowH - wRowFontSz) * 0.5f;
+                        float wMaxTextW = wPopupInnerW - wXZoneW - wTextPadX * 2.0f;
+                        std::string addrDisp = material::TruncateToWidth(addr, wRowFont, wRowFontSz, wMaxTextW);
                         pdl->AddText(wRowFont, wRowFontSz,
                             ImVec2(rowMin.x + wTextPadX, textY),
-                            isCurrent ? Primary() : OnSurface(), addr.c_str());
+                            isCurrent ? Primary() : OnSurface(), addrDisp.c_str());
                         // Tooltip for long addresses
                         if (rowHov && !inXZone)
                             material::Tooltip("%s", addr.c_str());