feat: DDEDIT command and double-click text editing

Add DDEDIT (ED alias) command that edits Text/MText/Attribute entities
in-place via the command line. Double-clicking a text entity in model space
now auto-launches DDEDIT for that entity. Supports Text, MText,
AttributeDefinition, and AttributeEntity types.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/annotate/ddedit.rs

@@ -0,0 +1,95 @@
+// DDEDIT — edit text content of a Text or MText entity in-place.
+//
+// Workflow:
+//   1. Pick a Text or MText entity (or fire from double-click with handle pre-set).
+//   2. Enter new text. Press Enter to commit, Escape to cancel.
+
+use acadrust::{EntityType, Handle};
+use glam::Vec3;
+
+use crate::command::{CadCommand, CmdResult};
+
+enum DdeditStep {
+    PickEntity,
+    EnterText { handle: Handle, current: String },
+}
+
+pub struct DdeditCommand {
+    step: DdeditStep,
+}
+
+impl DdeditCommand {
+    pub fn new() -> Self {
+        Self { step: DdeditStep::PickEntity }
+    }
+
+    /// Start with a pre-picked entity (for double-click use).
+    pub fn with_handle(handle: Handle, current: String) -> Self {
+        Self { step: DdeditStep::EnterText { handle, current } }
+    }
+}
+
+impl CadCommand for DdeditCommand {
+    fn name(&self) -> &'static str { "DDEDIT" }
+
+    fn prompt(&self) -> String {
+        match &self.step {
+            DdeditStep::PickEntity => "DDEDIT  Select text entity:".into(),
+            DdeditStep::EnterText { current, .. } => {
+                format!("DDEDIT  Enter new text <{current}>:")
+            }
+        }
+    }
+
+    fn needs_entity_pick(&self) -> bool {
+        matches!(self.step, DdeditStep::PickEntity)
+    }
+
+    fn on_entity_pick(&mut self, handle: Handle, _pt: Vec3) -> CmdResult {
+        if handle.is_null() { return CmdResult::NeedPoint; }
+        // The current value will be filled in by the caller (commands.rs dispatch)
+        // via on_text_input once the entity is known. Store handle here.
+        self.step = DdeditStep::EnterText { handle, current: String::new() };
+        CmdResult::NeedPoint
+    }
+
+    fn wants_text_input(&self) -> bool {
+        matches!(self.step, DdeditStep::EnterText { .. })
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let (handle, current) = match &self.step {
+            DdeditStep::EnterText { handle, current } => (*handle, current.clone()),
+            _ => return None,
+        };
+        // Empty input → keep existing text
+        let new_text = if text.trim().is_empty() { current } else { text.to_string() };
+        Some(CmdResult::DdeditEntity { handle, new_text })
+    }
+
+    fn on_point(&mut self, _pt: Vec3) -> CmdResult { CmdResult::NeedPoint }
+    fn on_enter(&mut self) -> CmdResult { CmdResult::Cancel }
+    fn on_escape(&mut self) -> CmdResult { CmdResult::Cancel }
+}
+
+/// Extract the text content from a Text or MText entity.
+pub fn entity_text(entity: &EntityType) -> Option<String> {
+    match entity {
+        EntityType::Text(t)  => Some(t.value.clone()),
+        EntityType::MText(t) => Some(t.value.clone()),
+        EntityType::AttributeDefinition(a) => Some(a.default_value.clone()),
+        EntityType::AttributeEntity(a)     => Some(a.get_value().to_string()),
+        _ => None,
+    }
+}
+
+/// Apply new text content to a cloned entity, returning the updated entity.
+pub fn set_entity_text(mut entity: EntityType, new_text: &str) -> Option<EntityType> {
+    match &mut entity {
+        EntityType::Text(t)  => { t.value = new_text.to_string(); Some(entity) }
+        EntityType::MText(t) => { t.value = new_text.to_string(); Some(entity) }
+        EntityType::AttributeDefinition(a) => { a.default_value = new_text.to_string(); Some(entity) }
+        EntityType::AttributeEntity(a)     => { a.set_value(new_text.to_string()); Some(entity) }
+        _ => None,
+    }
+}

src/modules/annotate/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod aligned_dim;
 pub mod angular_dim;
+pub mod ddedit;
 pub mod diameter_dim;
 pub mod dim_baseline;
 pub mod dim_continue;