feat(props): editable block Name row + collapsible XYZ groups

- Block reference Name (Misc) is editable: the dropdown re-points the
  insert to another definition; typing a new name renames the definition
  everywhere (record re-key, Block marker, every INSERT reference).
  Anonymous (*) and xref blocks stay read-only, with the same guards
  added to Scene::rename_block.
- Custom single-control dropdown (text field + caret) built on the
  shared floating_below overlay so the list always opens downward,
  unlike iced's space-based menu placement.
- Consecutive "<Base> X/Y/Z" rows (Position, Scale, Start, Center, ...)
  collapse into one expandable summary row across all entities; the
  expand state persists across rebuilds and selection changes.
- The BEDIT block tab no longer offers the layout Rename/Delete
  context menu.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scene/entity.rs

@@ -229,15 +229,30 @@ impl Scene {
 
     /// Rename a block definition: re-key its record, update the Block marker's
     /// name, and repoint every INSERT that referenced the old name so all
-    /// instances keep resolving. Returns false if `old` is missing, `new` is
-    /// already taken, or the names are equal (case-insensitive). (#261)
+    /// instances keep resolving. Returns false if `old` is missing or
+    /// anonymous/xref, `new` is invalid or already taken, or the names are
+    /// equal (case-insensitive). (#261)
     pub fn rename_block(&mut self, old: &str, new: &str) -> bool {
+        if !crate::scene::valid_block_name(new) {
+            return false;
+        }
         if old.eq_ignore_ascii_case(new) {
             return false;
         }
         if self.document.block_records.get(new).is_some() {
             return false;
         }
+        // Anonymous (*) names are program-owned and re-numbered on save; an
+        // xref('|') symbol name is bound to the referenced file.
+        if self
+            .document
+            .block_records
+            .get(old)
+            .map(|br| br.is_anonymous() || br.flags.is_xref || br.name.contains('|'))
+            .unwrap_or(true)
+        {
+            return false;
+        }
         let Some(mut br) = self.document.block_records.remove(old) else {
             return false;
         };

src/scene/mod.rs

@@ -204,6 +204,20 @@ pub fn vp_effective_scale(custom_scale: f64, view_height: f64, vp_height: f64) -
     1.0
 }
 
+/// A block name a user may assign: non-empty, no control characters, none of
+/// the symbol-table-reserved characters (`*` marks anonymous blocks, `|`
+/// xref-dependent ones; the rest are the DXF symbol-name exclusions).
+pub(crate) fn valid_block_name(name: &str) -> bool {
+    !name.is_empty()
+        && !name.chars().any(|c| {
+            c.is_control()
+                || matches!(
+                    c,
+                    '<' | '>' | '/' | '\\' | '"' | ':' | ';' | '?' | '*' | '|' | ',' | '=' | '`'
+                )
+        })
+}
+
 /// Pre-built entity caches returned by [`build_derived_caches`].
 /// Produced in the file-load background task so the UI thread only assigns.
 #[derive(Debug, Clone)]

src/scene/model/object.rs

@@ -17,6 +17,13 @@ pub enum PropValue {
         selected: String,
         options: Vec<String>,
     },
+    /// Editable text plus a dropdown of existing options (block reference
+    /// Name row): picking an option re-points the reference, submitting a
+    /// new name renames the definition.
+    EditChoice {
+        value: String,
+        options: Vec<String>,
+    },
     /// ACI/RGB/ByLayer/ByBlock color — rendered as a color picker.
     ColorChoice(AcadColor),
     /// Color varies across the current multi-selection.

src/scene/selection.rs

@@ -293,6 +293,7 @@ impl Scene {
                     PropValue::ReadOnly(s) | PropValue::EditText(s) => s,
                     PropValue::LayerChoice(s) => s,
                     PropValue::Choice { selected, .. } => selected,
+                    PropValue::EditChoice { value, .. } => value,
                     PropValue::ColorChoice(c) => Self::format_color(c),
                     PropValue::LwChoice(lw) => Self::format_lineweight(lw),
                     PropValue::LinetypeChoice(s) => s,