quality: cut dead-code false positives across C++, C#, XAML, tests

[RaghavChamadiya]

Summary

Five complementary fixes targeting the dominant false-positive buckets observed on desktop .NET / Win32 repositories. Probed against PowerToys; expected reductions estimated read-only from the existing index.

Fix	What it does	Estimated FP reduction on PowerToys
A	unused_export now treats an incoming calls / method_implements / reads edge on the symbol itself as evidence of life. Previously only file-level imported_names was checked.	C++ functions: −1,417
B	C++ void Foo::method() { … } now extracts with parent_name=Foo and kind=method. New cpp.scm pattern for two-level NS::Foo::method plus a parser helper that walks the qualified_identifier scope. Free functions unaffected.	C++ functions converted to method (non-importable): −1,674
C	dynamic_hints/dotnet.py learns typeof(TypeName) — covers [JsonConverter(typeof(X))], DataTemplate.DataType = typeof(X), manual DI registration.	C# class FPs: −144
D	dynamic_hints/xaml.py learns <prefix:TypeName …> element-tag references — catches converters, controls, templates declared as XAML elements. Property syntax (<Grid.Resources>) and bare built-in tags are excluded.	C# class FPs: −94
E	_NEVER_FLAG_PATTERNS adds test-project globs (*Tests/*.cs, *.UnitTests/*.cs, *FuzzTests/*.cs, *UITest*/*.cs, *Tests.cs, …) plus */unittests/*.cpp|.h.	Cross-language: −274 findings

Projected post-fix on PowerToys:

• C++ unused_export ≥0.7: 5,049 → ~1,200-1,500
• C# class unused_export ≥0.7: 1,240 → ~735-800
• Total dead-code findings: 9,015 → ~5,500

Test plan

• 550 ingestion / dead_code / pipeline / git tests passing (2 xfailed unchanged)
• New unit tests:
  • test_unused_export_skipped_when_symbol_has_incoming_calls
  • test_qualified_definition_binds_to_class (cpp Foo::DoOne, two-level NS::Bar::DoTwo)
  • test_typeof_type_emits_dynamic_uses, test_typeof_lowercase_local_ignored
  • test_element_tag_with_prefix_extracted, test_element_tag_property_syntax_skipped, test_bare_xaml_element_not_a_type_reference
• PowerToys re-index to verify estimated reductions