Retire legacy implementations and flatten managed layout

.gitignore

@@ -1,8 +1,8 @@
 # Build output
-/dotnet/**/bin/
-/dotnet/**/obj/
-/dotnet/**/TestResults/
-/dotnet/artifacts/
+**/bin/
+**/obj/
+**/TestResults/
+/artifacts/
 /build/
 /out/
 
@@ -19,7 +19,6 @@
 *.pdb
 
 # vcpkg (bundled as a submodule at /vcpkg — see docs/building.md §2)
-/vcpkg_installed/
 
 # Generated protobuf
 *.pb.cc
@@ -49,13 +48,8 @@ clients/apple/**/*.xcframework/
 clients/windows/**/bin/
 clients/windows/**/obj/
 # SwiftPM build artifacts
-clients/apple/.build/
-clients/apple/.swiftpm/
-clients/apple/Package.resolved
 
 # Test artifacts: TOFU pin store written by vc_client during headless tests
-# (core/src/core/client.cpp falls back to this relative path when tofu_store_path is unset).
 voicecat_tofu_pins.txt
 
 # Python bytecode cache (e.g. scripts/asc_api.py)
-__pycache__/