wx: fix layout — log adapts and stays at the bottom on resize

The frame had no sizer; it relied on the implicit single-child fill, which
didn't reliably resize the panel, so the panel's vertical sizer never
redistributed and the log kept its size when the window grew. Add a frame
sizer holding the panel at proportion 1 + wxEXPAND, so a resize re-lays-out
the panel and the log (1/3) tracks the window.

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

src/frontends/wx/wx_frame.cpp

@@ -170,6 +170,13 @@ EssimFrame::EssimFrame(WxFrontend &fe)
     root->Add(log_, 1, wxEXPAND | wxALL, 4);
     panel->SetSizer(root);
 
+    // Drive the panel from a frame sizer so it fills the client area and
+    // re-lays-out on every resize (the implicit single-child fill is not
+    // reliable here — without this the log keeps its size when the window grows).
+    auto *frame_sizer = new wxBoxSizer(wxVERTICAL);
+    frame_sizer->Add(panel, 1, wxEXPAND);
+    SetSizer(frame_sizer);
+
     Bind(wxEVT_MENU, &EssimFrame::OnLoad,    this, ID_LOAD);
     Bind(wxEVT_MENU, &EssimFrame::OnRestore, this, ID_RESTORE);
     Bind(wxEVT_MENU, &EssimFrame::OnSave,    this, ID_SAVE);