feat(block): BEDIT block editor as a dedicated space tab (#261)

Selecting a block and running BEDIT (command, ribbon button, or a
double-click on the block) opens a block-editor "space" tab, named after
the block, alongside Model/Layout in the status bar. The tab draws ONLY
the block record's own entities in block-local coordinates; edits are
live on the definition, so every INSERT updates. Save Block / Discard
buttons (side toolbar) finish the session; Discard restores the on-entry
snapshot. Space switching is locked while a block is open, and BEDIT and
REFEDIT are mutually exclusive.

Implementation: a Scene.block_edit_block override at the top of
current_layout_block_handle scopes render/pick/new-entity ownership to the
edited block while current_layout stays "Model" (so the pervasive
Model-vs-paper code keeps model behaviour). The model render/pick paths
that hardcoded model_space_block_handle (wire tile set, hatch render +
pick, block-instance meshes) are made binding-aware so the block isolation
actually takes effect and model content does not leak in. Entering fits
the camera to the block (fit_all already scopes via the binding). Renaming
the block tab renames the block itself — new Scene::rename_block re-keys
the record, updates the Block marker and repoints every INSERT reference.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/modules/draw/modify/block_edit.rs

@@ -0,0 +1,99 @@
+// BEDIT — block editor as a dedicated "space" tab (issue #261).
+//
+// Workflow:
+//   1. BEDIT: user picks an INSERT (or has one pre-selected).
+//   2. A block-editor space opens: rendering, picking and new geometry are
+//      scoped to the block's record, so ONLY the block's own (block-local)
+//      entities are drawn — no INSERT transform, they show exactly as stored.
+//   3. The user edits them with normal commands. Because they ARE the block
+//      definition's entities, edits are live.
+//   4. Save Block (BEDIT_SAVE): keep the edits and leave the block space.
+//      Discard (BEDIT_DISCARD): restore the block to its on-entry snapshot.
+//
+// Unlike REFEDIT (which copies entities into model space with the INSERT
+// transform and inverse-transforms them back on save), a BEDIT space edits the
+// block record in place, so there is no copy-back and no transform — the space
+// render filter (`current_layout_block_handle`) already draws only the block.
+
+use acadrust::{EntityType, Handle};
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdResult};
+use crate::modules::{IconKind, ModuleEvent, ToolDef};
+
+/// Right-edge side-toolbar buttons shown while a BEDIT block-editor space is
+/// active: save the block edits and leave, or discard them.
+pub fn block_edit_tools() -> Vec<ToolDef> {
+    vec![
+        ToolDef {
+            id: "BEDIT_SAVE",
+            label: "Save Block",
+            icon: IconKind::Svg(include_bytes!("../../../../assets/icons/mt_ok.svg")),
+            event: ModuleEvent::Command("BEDIT_SAVE".to_string()),
+        },
+        ToolDef {
+            id: "BEDIT_DISCARD",
+            label: "Discard Block Edit",
+            icon: IconKind::Svg(include_bytes!("../../../../assets/icons/mt_cancel.svg")),
+            event: ModuleEvent::Command("BEDIT_DISCARD".to_string()),
+        },
+    ]
+}
+
+// ── Session state (held in DocumentTab) ───────────────────────────────────
+
+/// Active BEDIT block-editor session. Lives in `DocumentTab::block_edit`.
+#[derive(Debug, Clone)]
+pub struct BlockEditSession {
+    /// Name of the block being edited (also the space-tab label).
+    pub block_name: String,
+    /// Handle of the block record whose entities are being edited.
+    pub br_handle: Handle,
+    /// Space to return to when the block editor closes (the layout that was
+    /// active when BEDIT began).
+    pub return_layout: String,
+    /// The block's block-local entities captured on entry, so Discard can
+    /// restore the definition (structural Block/BlockEnd/AttDef excluded).
+    pub snapshot: Vec<EntityType>,
+}
+
+// ── BEDIT pick command ─────────────────────────────────────────────────────
+
+/// Step 1: wait for the user to pick a single INSERT entity to edit.
+pub struct BlockEditPickCommand;
+
+impl BlockEditPickCommand {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl CadCommand for BlockEditPickCommand {
+    fn name(&self) -> &'static str {
+        "BEDIT"
+    }
+    fn prompt(&self) -> String {
+        "BEDIT  Select block reference to edit:".into()
+    }
+    fn needs_entity_pick(&self) -> bool {
+        true
+    }
+    fn on_entity_pick(&mut self, handle: Handle, _pt: DVec3) -> CmdResult {
+        if handle.is_null() {
+            return CmdResult::NeedPoint;
+        }
+        // Signal the host to open the block-editor space for this INSERT.
+        CmdResult::Relaunch(format!("BEDIT_BEGIN:{}", handle.value()), vec![handle])
+    }
+    fn on_point(&mut self, _pt: DVec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+}
+
+// ── Autocomplete registry ─────────────────────────────────
+inventory::submit!(crate::command::CommandRegistration { names: &["BEDIT"] }); // BlockEditPickCommand
+inventory::submit!(crate::command::CommandRegistration { names: &["BEDIT_SAVE"] });
+inventory::submit!(crate::command::CommandRegistration { names: &["BEDIT_DISCARD"] });

src/modules/draw/modify/mod.rs

@@ -11,6 +11,7 @@ pub mod lengthen;
 pub mod mirror;
 pub mod offset;
 pub mod pedit;
+pub mod block_edit;
 pub mod refedit;
 pub mod reverse;
 pub mod rotate;