ci: add tag-triggered release packaging workflow

Adds .gitea/workflows/release.yml, triggered only on a pushed v* tag, which
builds all three platforms (reusing the exact same configure/build/test
commands as build.yml, now factored out into .gitea/scripts/ so the two
workflows can't drift), zips each platform's build/package/ output, and
creates a draft Gitea Release with the archives attached.

This is packaging automation only -- it does not resolve or bypass the C1
WebRTC/OpenH264 release gate documented in README.md's Status section.
Nothing publishes until a human deliberately pushes a version tag (which
should not happen before owner sign-off) and then explicitly publishes the
resulting draft. The generated release notes lead with a restatement of the
open C1 question specifically so that second step can't be taken by
accident.

build.yml is refactored (not rewritten) to call the same shared scripts;
its job/step behavior is otherwise unchanged.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RL8abRmgFXkVASHkkqiJbE

.gitea/scripts/windows-build.ps1

@@ -0,0 +1,38 @@
+# Shared with .gitea/workflows/build.yml and .gitea/workflows/release.yml --
+# this is the actual Windows configure/build/test/verify sequence. Edit once,
+# here, so both workflows stay in sync instead of drifting copies.
+#
+# The default Visual Studio generator is required, not Ninja:
+# cmake/windows/buildspec.cmake keys the dependency slice off
+# CMAKE_VS_PLATFORM_NAME, which only a VS generator sets.
+#
+# Same fallback as macOS, and the same warning: a green job that quietly
+# stopped building the plugin is worse than a red one. PowerShell, not bash:
+# self-hosted Windows runners here cannot be assumed to have a working bash
+# (WSL as local system is refused).
+
+cmake -S . -B build -A x64
+if ($LASTEXITCODE -ne 0) {
+  Write-Host "::warning::OBS SDK bootstrap failed on Windows; building the core library only. The plugin module was NOT built."
+  Remove-Item -Recurse -Force build -ErrorAction SilentlyContinue
+  cmake -S . -B build -A x64 -DSTPLUGIN_BOOTSTRAP_OBS=OFF
+  if ($LASTEXITCODE -ne 0) { exit 1 }
+}
+
+cmake --build build --config Release
+
+ctest --test-dir build -C Release --output-on-failure
+
+# Show what was built.
+#
+# This is not purely informational: the from-source libobs bootstrap is
+# expected to work reliably on this runner (that is the whole point of the
+# buildspec bootstrap + find_package fix), so a missing module here is a
+# regression to fail loudly on, not the old silent fallback.
+$module = "build\package\bin\64bit\streamer-tools-camera.dll"
+if (Test-Path $module) {
+  Get-ChildItem build\package\bin\64bit
+} else {
+  Write-Host "::error::no plugin module was built -- $module is missing. The Windows from-source libobs bootstrap is expected to succeed; treat this as a build failure, not a core-library-only fallback."
+  exit 1
+}