feat(scan): recognize qualified Rust functions

docs/architecture/language-support.md

@@ -14,7 +14,7 @@ contracts and fixtures reach the same standard.
 | Language | Useful current coverage | Important gaps | Tier |
 | --- | --- | --- | --- |
 | Dart | Classes, mixins, enums, extensions, many methods, imports, `extends`, and ordinary calls | `with`/`implements`, export/part, named constructors, accessors/operators, and multiline declarations | first-class target |
-| Rust | Structs, enums, traits, ordinary/async functions, simple `use`, calls, and raw-string masking | impl/module ownership, const/unsafe/extern functions, macros, turbofish calls, and braced/glob imports | first-class target |
+| Rust | Structs, enums, traits, ordinary/async/const/unsafe/extern functions, simple `use`, calls, and raw-string masking | impl/module ownership, unions/type aliases, macros, turbofish calls, and braced/glob imports | first-class target |
 | C | Files, basic includes, structs, and narrow function forms through the shared C/C++ profile | distinct C identity, enums/typedefs/function pointers, multiline declarations, macros, and declaration masking | first-class target |
 | C++ | Basic classes/structs, narrow function forms, calls, and local include resolution | templates, constructors/destructors/operators, multiple inheritance, namespaces, overloads, lambdas, qualifiers, and multiline declarations | first-class target |
 | JavaScript | Named functions, simple classes/extends, ES imports, and call-shaped expressions | methods, arrows/function expressions, CommonJS, dynamic imports, re-exports, decorators, and template literals | first-class target |

src/scan.rs

@@ -585,7 +585,7 @@ impl Patterns {
             ),
             "rust" => (
                 r"^\s*(?:pub(?:\([^)]*\))?\s+)?(?:struct|enum|trait)\s+(?P<name>[A-Za-z_]\w*)",
-                r"^\s*(?:pub(?:\([^)]*\))?\s+)?(?:async\s+)?fn\s+(?P<name>[A-Za-z_]\w*)\s*(?:<[^>]*>)?\s*\(",
+                r#"^\s*(?:pub(?:\([^)]*\))?\s+)?(?:(?:const|async|unsafe)\s+)*(?:extern(?:\s+"[^"]+")?\s+)?fn\s+(?P<name>[A-Za-z_]\w*)\s*(?:<[^>]*>)?\s*\("#,
                 r"^\s*use\s+(?P<name>[A-Za-z_][\w:]*)",
             ),
             "javascript" | "typescript" => (

tests/fixtures/languages/rust/basic.rs

@@ -7,3 +7,11 @@ pub fn start() {
 }
 
 fn helper() {}
+
+pub const fn constant() -> usize {
+    1
+}
+
+pub unsafe fn unsafe_op() {}
+
+pub extern "C" fn ffi_entry() {}

tests/language_parity.rs

@@ -28,7 +28,7 @@ fn first_class_language_fixtures_have_stable_baseline_evidence() {
             directory: "rust",
             language: "rust",
             classes: &["Worker"],
-            functions: &["helper", "start"],
+            functions: &["constant", "ffi_entry", "helper", "start", "unsafe_op"],
             imports: 1,
             inherits: 0,
             calls: 1,