fix(gui): limit Files & Media collapsible child height to reasonable max

The begin_child() was using (0, -40) which made it stretch to fill parent.
Changed to (0, min(len(items) * 30 + 50, 300)) so it:
- Sizes to content (30px per row + 50px header)
- Caps at 300px max height
- Allows scrolling when content overflows

src/gui_2.py

@@ -2921,7 +2921,7 @@ def hello():
    r.destroy()
    if d: self.ui_files_base_dir = d
   imgui.separator()
-  imgui.begin_child("f_paths", imgui.ImVec2(0, -40), True)
+  imgui.begin_child("f_paths", imgui.ImVec2(0, min(len(self.files) * 30 + 50, 300)), True)
   if imgui.begin_table("files_table", 4, imgui.TableFlags_.resizable | imgui.TableFlags_.borders):
    imgui.table_setup_column("Actions", imgui.TableColumnFlags_.width_fixed, 40)
    imgui.table_setup_column("File Path", imgui.TableColumnFlags_.width_stretch)
@@ -2994,7 +2994,7 @@ def hello():
    r.destroy()
    if d: self.ui_shots_base_dir = d
   imgui.separator()
-  imgui.begin_child("s_paths", imgui.ImVec2(0, -40), True)
+  imgui.begin_child("s_paths", imgui.ImVec2(0, min(len(self.screenshots) * 30 + 50, 300)), True)
   for i, s in enumerate(self.screenshots):
    if imgui.button(f"x##s{i}"):
     self.screenshots.pop(i)