Fix crate-name import resolution for bin+lib crates

Register the Cargo package name (normalized - -> _) as an alias for
src/lib.rs in the resolver, so 'use <crate>::{...}' in src/main.rs
resolves to src/lib.rs. Adds rustdemo/Cargo.toml fixture and test
coverage; updates blast-radius test for the new transitive edge.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/cli.rs

@@ -90,6 +90,22 @@ fn rust_index_search_and_dead() {
         "source contains function body"
     );
 
+    // `use rustdemo::add` in main.rs resolves via the package-name alias.
+    let importers = run_json(&[
+        "--project",
+        fx.to_str().unwrap(),
+        "find",
+        "importers",
+        "src/lib.rs",
+    ]);
+    let names: Vec<&str> = importers
+        .as_array()
+        .unwrap()
+        .iter()
+        .map(|v| v.as_str().unwrap())
+        .collect();
+    assert!(names.contains(&"src/main.rs"), "main.rs imports lib.rs");
+
     // dead.rs is flagged; entry points lib.rs/main.rs are not.
     let dead = run_json(&["--project", fx.to_str().unwrap(), "find", "dead"]);
     let paths: Vec<&str> = dead["files"]
@@ -118,7 +134,7 @@ fn inspect_blast_radius_finds_affected_files() {
         "blast-radius",
         "src/util.rs",
     ]);
-    assert_eq!(blast["count"], 1);
+    assert_eq!(blast["count"], 2);
     assert_eq!(blast["file"], "src/util.rs");
     let affected: Vec<&str> = blast["affected"]
         .as_array()
@@ -126,7 +142,9 @@ fn inspect_blast_radius_finds_affected_files() {
         .iter()
         .map(|f| f["path"].as_str().unwrap())
         .collect();
-    assert_eq!(affected, ["src/lib.rs"], "lib.rs imports util.rs");
+    // lib.rs imports util.rs directly; main.rs reaches it via the crate name.
+    assert!(affected.contains(&"src/lib.rs"), "lib.rs imports util.rs");
+    assert!(affected.contains(&"src/main.rs"), "main.rs → lib.rs → util.rs");
 }
 
 #[test]