chore: drop legacy comments and the last unused dead_code allows

* io/xref.rs — replaced the 7-line "BlockRecord::is_loaded turned out to
  be unreliable" rationale with a one-liner. The reverted experiment
  lives in git history (e88a946, 0996b75).
* refedit::RefEditSession.insert_handle — set at construction but never
  read; the "kept for future REFCLOSE DISCARD" TODO can come back via
  git history when that feature lands.
* scene::mod — dropped the placeholder MeshModel re-export; nothing
  outside `mesh_model` consumes the bare name and MeshLodSet is the
  pipeline-facing type now.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/app/commands.rs

@@ -1890,7 +1890,6 @@ impl H7CAD {
                 }
 
                 let session = RefEditSession {
-                    insert_handle,
                     block_name: insert.block_name.clone(),
                     br_handle,
                     temp_handles: vec![],

src/io/xref.rs

@@ -37,15 +37,7 @@ pub struct XrefInfo {
 ///
 /// Returns a list of [`XrefInfo`] describing each xref block found.
 pub fn resolve_xrefs(doc: &mut CadDocument, base_dir: &Path) -> Vec<XrefInfo> {
-    // Collect xref blocks: (name, raw_path, block_record_handle)
-    //
-    // Note: `BlockRecord::is_loaded` (the DWG R2000+ "loaded" bit) turned out
-    // to be unreliable as a signal of AutoCAD's Unload state — different
-    // files with xrefs the manager calls "Loaded" carry both `Some(true)`
-    // and `Some(false)` on disk. Until we identify the actual on-disk
-    // representation of XREF→Unload (likely in an XREF dependency record
-    // or ACAD_XREF_PANEL_DATA xrecord), we auto-resolve every xref and
-    // rely on frustum culling to keep the GPU bounded.
+    // Auto-resolve every xref — frustum + LOD culling keep GPU cost bounded.
     let xref_entries: Vec<(String, String, Handle)> = doc
         .block_records
         .iter()

src/modules/home/modify/refedit.rs

@@ -23,9 +23,6 @@ use crate::command::{CadCommand, CmdResult};
 /// Active REFEDIT session.  Lives in `DocumentTab::refedit_session`.
 #[derive(Debug, Clone)]
 pub struct RefEditSession {
-    /// The INSERT entity being edited (kept for future REFCLOSE DISCARD).
-    #[allow(dead_code)]
-    pub insert_handle: Handle,
     /// Name of the block being edited.
     pub block_name: String,
     /// Handle of the block record (owns the block entities).

src/scene/mod.rs

@@ -28,8 +28,6 @@ pub use camera::Projection;
 pub use hatch_model::HatchModel;
 pub use image_model::ImageModel;
 pub use mesh_model::MeshLodSet;
-#[allow(unused_imports)]
-pub use mesh_model::MeshModel;
 pub use object::{GripApply, GripDef};
 pub use pipeline::uniforms::Uniforms;
 pub use pipeline::viewcube::{hit_test, CubeRegion, VIEWCUBE_DRAW_PX, VIEWCUBE_PAD, VIEWCUBE_PX};