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/model/object.rs

@@ -8,6 +8,8 @@ use glam::DVec3;
 pub enum PropValue {
     /// Read-only display text.
     ReadOnly(String),
+    /// Read-only display text with a tooltip explaining why it cannot be edited.
+    ReadOnlyWithTooltip { value: String, tooltip: String },
     /// Editable numeric field.
     EditText(String),
     /// Editable text that must not be expression-evaluated.