M14: add Windows 7 SP1 x64 compatibility build

docs/windows7.md

@@ -0,0 +1,71 @@
+# Windows 7 x64 compatibility build (experimental)
+
+This separate build targets **64-bit Windows 7 SP1**. It uses OpenGL instead of wgpu,
+and omits the native AccessKit accessibility adapter. Printer discovery supports the
+PowerShell version included with Windows 7, and printer setup opens Control Panel.
+The normal desktop and web builds retain their existing defaults. A vendor graphics driver providing **OpenGL 3.3 or newer**
+is required; the Windows built-in generic display driver is insufficient. GPU selection
+in Preferences and `WGPU_POWER_PREF` do not control this OpenGL build.
+
+## Build or download
+
+In your GitHub fork, open **Actions → Windows 7 x64 compatibility → Run workflow**.
+When it succeeds, download the `vectorcraft-windows7-x64-portable` artifact, extract the
+contained portable ZIP, then run `vectorcraft.exe` on Windows 7. The CLI is included.
+No MSI is provided: the existing installer remains for modern Windows.
+
+To build locally, use a **Windows 10/11 build computer**, with Rust/rustup and Visual Studio
+2022 C++ build tools (x64 compiler and Windows SDK). Open an **x64 Native Tools Command
+Prompt for VS 2022**, change to your clone's repository root (the directory containing
+`Cargo.toml`), and run:
+
+```powershell
+powershell -ExecutionPolicy Bypass -File packaging/windows/windows7.ps1
+```
+
+Output: `dist/release/vectorcraft-windows7-x64-portable.zip`. The script installs the pinned
+nightly compiler and `rust-src`, rebuilds the standard library for
+`x86_64-win7-windows-msvc`, and links the C runtime statically. It never installs Rust on
+the Windows 7 machine. The optional `CRAFT_FONTS_DIR` setting works as in the normal build.
+Without it, install fonts for the languages you need on the destination machine.
+
+The Windows 7 target matters: modern Rust's ordinary `x86_64-pc-windows-msvc` target
+requires Windows 10, including standard-library and random-number APIs. Selecting OpenGL
+alone or changing an installer version check cannot fix that.
+
+References: [Rust's Windows 7 target](https://doc.rust-lang.org/rustc/platform-support/win7-windows-msvc.html)
+and [Windows baseline change](https://blog.rust-lang.org/2024/02/26/Windows-7/).
+
+The packaging script checks x64 PE headers, the subsystem version, and known incompatible
+imports (including `GetSystemTimePreciseAsFileTime`) before creating the ZIP. This is a
+regression check, not an exhaustive audit of every Windows API.
+
+The small vendored `windows-link` patch routes `CoTaskMemFree` to its documented
+`ole32.dll` export on the Windows 7 target; the newer binding otherwise imports
+`combase.dll`, which is absent on Windows 7. Other targets keep upstream behavior.
+
+## Runtime validation
+
+A user confirmed that the portable x64 compatibility build runs on Windows 7 SP1
+with an NVIDIA graphics card. Their original build failed at startup with
+`GetSystemTimePreciseAsFileTime` missing from `kernel32.dll`; the compatibility
+build resolved that failure. The tested build was based on upstream commit
+`1f7873273b67007b0aefc63313e0d34a39f45453`. The exact GPU/driver version and completion
+of every checklist item below were not recorded, so support remains experimental.
+
+## Runtime acceptance checklist
+
+A successful build on the Windows 2022 CI runner does **not** prove Windows 7 runtime
+compatibility. Before declaring support, test on a Windows 7 SP1 x64 machine and record
+its GPU, driver version, Windows updates and any missing-DLL/entry-point error:
+
+- Start `vectorcraft.exe`; verify a visible canvas, resizing, minimize/restore and exit.
+- Draw a shape, save a `.vectorcraft` document, close and reopen it.
+- Open `examples/dusk-poster.vectorcraft`; export PNG and PDF and inspect both.
+- Exercise native Open/Save dialogs, clipboard text/images and drag-and-drop.
+- Change a preference, exit and verify it survives restarting.
+- Run `vectorcraft-cli.exe --version` and a headless export from a Command Prompt in the
+  extracted application folder.
+
+This build is experimental until that checklist passes. New dependency versions can add
+newer Windows imports, so retain Cargo.lock and repeat runtime QA after dependency updates.