feat(block): fade context, free editing and a Save/Discard toolbar in REFEDIT

In-place block edit now reads more like a dedicated editor:

- Fade everything except the edited entities toward the background (wires,
  block instances and 3D solid meshes) so the block stands out while the
  surrounding drawing stays visible for context.
- Don't leave a command active on enter — the user edits the block's geometry
  freely (move, grips, draw, erase) and finishes explicitly.
- Show the right-edge vertical toolbar with clickable Save (REFCLOSE_SAVE) and
  Discard (REFCLOSE_DISCARD) buttons while a session is active, so the edit
  can be ended without typing.

The fade clears on save/discard, restoring full brightness.

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

src/modules/draw/modify/refedit.rs

@@ -17,6 +17,26 @@ use acadrust::{EntityType, Handle};
 use glam::Vec3;
 
 use crate::command::{CadCommand, CmdResult};
+use crate::modules::{IconKind, ModuleEvent, ToolDef};
+
+/// Right-edge side-toolbar buttons shown while a REFEDIT session is active:
+/// save the in-place block edit, or discard it. (#136)
+pub fn refedit_tools() -> Vec<ToolDef> {
+    vec![
+        ToolDef {
+            id: "REFCLOSE_SAVE",
+            label: "Save Block Edit",
+            icon: IconKind::Svg(include_bytes!("../../../../assets/icons/mt_ok.svg")),
+            event: ModuleEvent::Command("REFCLOSE_SAVE".to_string()),
+        },
+        ToolDef {
+            id: "REFCLOSE_DISCARD",
+            label: "Discard Block Edit",
+            icon: IconKind::Svg(include_bytes!("../../../../assets/icons/mt_cancel.svg")),
+            event: ModuleEvent::Command("REFCLOSE_DISCARD".to_string()),
+        },
+    ]
+}
 
 // ── Session state (held in DocumentTab) ───────────────────────────────────