perf(overview): clip the address list to the visible rows

The Overview address list built all N rows on every frame (icons,
labels, balances, buttons, an InvisibleButton and a context-menu
check per address) and allocated a vector of N row positions, however
few rows fit on screen; the edge mask then walked all their vertices.

An ImGuiListClipper now submits only the rows that intersect the
list's clip rect, plus:
- one guard row on each side, so dividers and anti-aliased edges at
  the clip boundary are drawn as before;
- the row being dragged and the row whose context menu is open, so
  drag-to-reorder and the menu keep working when they scroll away;
- the rows keyboard navigation targets (kept by the clipper itself).

Before each row the cursor is put back exactly where the unclipped
loop left it, so the density-scaled spacing, which depends on the
cursor position, and every row's geometry are unchanged. Row tops are
computed from the index, so the per-frame vector is gone, and the
scroll extent is the same. The row model (sort, filter) is still
rebuilt over all addresses each frame.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/windows/balance_address_list.h

@@ -63,5 +63,18 @@ AddressRowLayout ComputeAddressRowLayout(float rowX,
                                          float spacingXs);
 std::string FormatAddressUsdValue(double balance, double priceUsd);
 
+// ---- Overview address-list clipping (fixed row pitch rowH from startY) ----
+// [begin, end) = the rows intersecting [clipMinY, clipMaxY) plus ONE guard row on each side (a row draws its
+// divider / AA fringe just past its own slot), clamped to [0, rowCount). Non-finite input -> every row.
+struct AddressRowWindow {
+    int begin = 0;
+    int end = 0;
+};
+AddressRowWindow ComputeAddressRowWindow(float clipMinY, float clipMaxY, float startY, float rowH, int rowCount);
+// Cursor y the unclipped row loop had when row i's body ran: row 0 = startY; row i > 0 = where ImGui::ItemSize
+// (imgui 1.92.6) leaves it after row i-1's InvisibleButton(h = rowH) placed at startY + (i-1)*rowH, i.e.
+// IM_TRUNC(top + rowH + ItemSpacing.y). Replaying it keeps the cursor-dependent Layout::spacing*() exact.
+float AddressRowEntryCursorY(int i, float startY, float rowH, float itemSpacingY);
+
 } // namespace ui
 } // namespace dragonx