chore: expose lib target + open-path profiling examples

Examples can't import from a bin-only crate, so add a thin lib.rs that
re-exports the existing modules. Used by the new examples that helped
diagnose the freeze fixed in the previous commit.

- examples/time_open: times parse / purge / cache / first-wires phases
- examples/inspect_insert: lists Insert blocks with sub-entity counts
- examples/find_raster: dumps RasterImage path + dimensions

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

examples/inspect_insert.rs

@@ -0,0 +1,43 @@
+// Lists every Insert in the doc (after xref resolve) with sub-entity counts.
+// cargo run --release --example inspect_insert -- <dwg>
+use acadrust::entities::EntityType;
+use acadrust::io::dwg::DwgReader;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let path = std::env::args().nth(1).unwrap();
+    let mut doc = DwgReader::from_file(&path)?.read()?;
+    if let Some(base) = std::path::Path::new(&path).parent() {
+        let infos = H7CAD::io::xref::resolve_xrefs(&mut doc, base);
+        for i in &infos {
+            println!("XREF: {} -> {:?}", i.name, i.status);
+        }
+    }
+    println!("total entities: {}", doc.entities().count());
+
+    let inserts: Vec<_> = doc
+        .entities()
+        .filter_map(|e| if let EntityType::Insert(i) = e { Some(i.clone()) } else { None })
+        .collect();
+    println!("total inserts: {}", inserts.len());
+
+    let mut by_block: std::collections::HashMap<String, usize> = std::collections::HashMap::new();
+    for i in &inserts {
+        *by_block.entry(i.block_name.clone()).or_insert(0) += 1;
+    }
+    let mut by_block: Vec<_> = by_block.into_iter().collect();
+    by_block.sort_by(|a, b| b.1.cmp(&a.1));
+
+    println!("\ninserts grouped by block_name:");
+    for (name, n) in &by_block {
+        let sub_count = inserts.iter().find(|i| &i.block_name == name)
+            .map(|i| i.explode_from_document(&doc).len())
+            .unwrap_or(0);
+        let nested = doc.block_records.get(name)
+            .map(|br| br.entity_handles.iter()
+                .filter(|h| matches!(doc.get_entity(**h), Some(EntityType::Insert(_))))
+                .count())
+            .unwrap_or(0);
+        println!("  {:>4} × {}  (sub={}, nested-inserts={})", n, name, sub_count, nested);
+    }
+    Ok(())
+}