Language bindings, KDE thumbnails, yapf compare, in-memory encoding

- yapf_encode() / yapf_free_buffer(): encode to memory; yapf_save uses it
- yapf.c also compiles as C++
- `yapf compare`: size and decode speed of the original format vs YAPF,
  with a lossless check
- bindings with tested examples: C++ (header-only), C# (P/Invoke),
  Rust (crate, builds the C code), Go (cgo), Java (FFM API, Java 22+),
  Zig (@cImport), LuaJIT (FFI), TypeScript types for the JS port;
  Python now encodes in memory
- docs/LANGUAGES.md and examples/ with measured results
- KDE Dolphin thumbnail plugin (KF6, CMake)
- README: honest status for Photoshop / VS Code / Figma (not run in the
  apps yet) and macOS (cross-compiled only), platform table

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

extensions/kde/kde-shell.nix

@@ -0,0 +1,6 @@
+# Development shell for building the plugin on NixOS: nix-shell kde-shell.nix
+with import <nixpkgs> {};
+mkShell {
+  nativeBuildInputs = [ cmake kdePackages.extra-cmake-modules pkg-config ];
+  buildInputs = [ kdePackages.kio kdePackages.qtbase kdePackages.kcoreaddons ];
+}