Add tool_win32: manifest-driven Win32 namespace orchestration tool

[Copilot]

Adds tool_win32 — a new binary crate that drives the full pipeline for compiling Win32 SDK headers namespace-by-namespace into a merged Windows.Win32.winmd, as outlined in issue #4300.

New crate: crates/tools/win32

• src/manifest.rs — TOML manifest structs (Manifest, Namespace) deserialized via serde
• src/main.rs — CLI + three-step per-namespace pipeline:
  1. Clang::write() → per-namespace .rdl
  2. Reader::write() → per-namespace .winmd
  3. Merger::merge() → combined Windows.Win32.winmd
• example.toml — example manifest covering Foundation, System.Com, and UI.WindowsAndMessaging

Manifest format

args = ["--target=x86_64-pc-windows-msvc", "-fms-extensions", "-DWIN32_LEAN_AND_MEAN"]
# reference = "path/to/Windows.Win32.winmd"  # cross-namespace type resolution

[[namespace]]
name    = "Windows.Win32.Foundation"
library = "kernel32"
headers = ["um/WinBase.h", "shared/winerror.h"]
filters = ["WinBase.h", "winerror.h"]

[[namespace]]
name    = "Windows.Win32.System.Com"
library = "ole32"
headers = ["um/ObjIdl.h"]

CLI

Usage: tool_win32 <manifest.toml> [OPTIONS]

Options:
  -o, --output <dir>        Output directory for .rdl/.winmd files [default: target/win32]
  -r, --reference <file>    Reference .winmd for cross-namespace type resolution
  -I, --include <dir>       SDK include directory (repeatable)
      --merge-output <name> Merged output filename [default: Windows.Win32.winmd]
  -k, --keep-going          Continue after per-namespace errors

[kennykerr]

@copilot fmt

[Copilot]

@copilot fmt

Done in acaa8ed.