feat(properties): make inherited properties editable, align dropdowns, and switch transparency to EditChoice

Enable in-place editing of inherited properties in the Properties panel:
- Transparency: Switch to PropValue::EditChoice with ByLayer and ByBlock presets to allow direct typing of any numeric percentage value (0..90%) without combo_box autocomplete interference.
- Select-all-on-click: Integrate EditChoice text inputs into build_field_key_map with dedicated widget IDs, preserving click-to-select-all across editable fields.
- Material: Provide bounded preset choices (ByLayer, ByBlock, Global, and active custom material) to avoid scanning large drawing dictionaries.
- Plot style: Implement mode-aware behavior with interactive Choice in STB mode and ReadOnlyWithTooltip in CTB mode.
- Read-only tooltips: Introduce PropValue::ReadOnlyWithTooltip to provide contextual explanations for locked fields while preserving mouse text selection and clipboard copying.
- Dropdown alignment & unified borders: Fix EditChoice internal input/caret background clipping so the container's 1px neutral/active border surrounds the entire control identically to Lineweight and text inputs.
- Document defaults & aggregation: Synchronize document header defaults when editing with No selection, and aggregate heterogeneous multi-selections (*VARIES*).

src/scene/selection.rs

@@ -463,6 +463,7 @@ impl Scene {
                             match prop.value {
                                 PropValue::PlainText(_) => QSelectValueEditor::Text,
                                 PropValue::ReadOnly(ref value)
+                                | PropValue::ReadOnlyWithTooltip { ref value, .. }
                                 | PropValue::EditText(ref value) => {
                                     let field = prop.field.to_ascii_lowercase();
                                     let textual = [
@@ -660,6 +661,7 @@ impl Scene {
                     .find(|p| p.field == field)?;
                 Some(match prop.value {
                     PropValue::ReadOnly(s)
+                    | PropValue::ReadOnlyWithTooltip { value: s, .. }
                     | PropValue::EditText(s)
                     | PropValue::PlainText(s) => s,
                     PropValue::LayerChoice(s) => s,