Add missing RmlUiComponent base class

The picker windows in rmlui_fields.lua were extending RmlUiComponent,
but this base class was never defined, causing potential runtime errors.

Added rmlui_component.lua with a simple base class for RmlUi components
that don't need full dialog functionality (OK/Cancel buttons, etc.).

This class provides:
- Initialize() for loading RML documents
- Show()/Hide()/Close() for visibility control
- Simple title element support

Author: claude

scen_edit/view/rmlui_component.lua

@@ -0,0 +1,65 @@
+--- RmlUi Base Component
+--- Simpler base class for RmlUi windows/components that aren't full dialogs
+--- (pickers, floating windows, etc.)
+
+RmlUiComponent = LCS.class{}
+
+function RmlUiComponent:init(rmlPath, title)
+    self.rmlPath = rmlPath
+    self.title = title or "Component"
+    self.document = nil
+    self.visible = false
+end
+
+function RmlUiComponent:Initialize()
+    if not SB.rmlui or not SB.rmlui.initialized then
+        Log.Warning("RmlUi not initialized")
+        return false
+    end
+
+    -- Load document
+    self.document = SB.rmlui:LoadDocument(self.rmlPath, false)
+    if not self.document then
+        Log.Error("Failed to load component: " .. self.rmlPath)
+        return false
+    end
+
+    -- Set title if there's a title element
+    local titleElement = self.document:GetElementById("component-title")
+    if titleElement then
+        titleElement.inner_rml = self.title
+    end
+
+    Log.Notice(self.title .. " component initialized")
+    return true
+end
+
+function RmlUiComponent:Show()
+    if not self.document then
+        if not self:Initialize() then
+            return
+        end
+    end
+
+    self.document:Show()
+    self.visible = true
+end
+
+function RmlUiComponent:Hide()
+    if self.document then
+        self.document:Hide()
+        self.visible = false
+    end
+end
+
+function RmlUiComponent:Close()
+    if self.document then
+        self.document:Close()
+        self.document = nil
+        self.visible = false
+    end
+end
+
+function RmlUiComponent:IsVisible()
+    return self.visible
+end

scen_edit/view/view.lua

@@ -52,6 +52,7 @@ function View:InitializeRmlUi()
     SB.Include(Path.Join(SB.DIRS.SRC, 'view/rmlui_floating/top_left_menu.lua'))
 
     -- Load RmlUi field system (maintains original AddField API - implementation-agnostic!)
+    SB.Include(Path.Join(SB.DIRS.SRC, 'view/rmlui_component.lua'))  -- Base class for components
     SB.Include(Path.Join(SB.DIRS.SRC, 'view/rmlui_editor_base.lua'))
     SB.Include(Path.Join(SB.DIRS.SRC, 'view/rmlui_fields.lua'))
     SB.Include(Path.Join(SB.DIRS.SRC, 'view/rmlui_field_compat.lua'))  -- Makes StringField() etc work