Add continuous Windows release workflow and runner docs

Public repo already; workflow builds portable zip on windows-release
and publishes windows-continuous. Bump linux Conan profile to gcc 16.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/windows-runner.md

@@ -0,0 +1,24 @@
+# Windows Forgejo runner (`windows-release`)
+
+Tower dual-boots Windows. Native InfiniPaint Windows builds need **MSVC 2022**
+(see `docs/BUILDING.md` + `windowsinstall/`). There is no Linux cross-build path.
+
+## One-time setup (on Windows)
+
+1. Install Visual Studio 2022 Build Tools (C++), CMake, Git, Python 3.
+2. `pip install "conan>=2,<3"`.
+3. Download [forgejo-runner](https://code.forgejo.org/forgejo/runner/releases) for Windows.
+4. Register against `https://forgejo.fsociety00.cc` with label **`windows-release`**
+   (repo or org runner; Actions must be enabled — already on for `copilot/infinipaint`).
+5. Run the runner as a service or in a logged-on session when you want CI to drain.
+
+## Behaviour
+
+Workflow: `.forgejo/workflows/windows_release.yml`
+
+- Triggers on every push to `main` (and `workflow_dispatch`)
+- Builds x86_64 portable zip via `windowsinstall/*_x86_64.bat`
+- Publishes/updates prerelease tag **`windows-continuous`**
+
+Jobs stay queued in Forgejo until a `windows-release` runner is online
+(same pattern as `desktop-release` capacity/queue on Tower Linux).