ci: Gitea pipeline — gate on both self-hosted runners, publish alpha releases

Every push to main now runs the gate on the self-hosted runners and, when
green, publishes a Gitea Release carrying the client, launcher+bake, and
manifest.

Pipeline (.gitea/workflows/ci.yml):
- windows-gate runs tools/run-release-gate.ps1, the project's own bounded
  gate. A bare `dotnet test AcDream.slnx` is NOT usable as a gate: it fails
  ~36 tests by design, because the InstalledDat/Live/Manual/OS lanes assert
  their own preconditions. The gate script's trait filter is what excludes
  them.
- linux-portable runs the portable closure, where the Linux-lane tests
  actually execute instead of failing on Windows.
- release depends on both, so a red gate cannot publish. It is a job in the
  same workflow rather than a workflow_run trigger, whose Forgejo support is
  unreliable; `needs` is guaranteed.

No actions/setup-dotnet: data.forgejo.org does not mirror it at all (404),
and both runners carry the pinned SDK band already. actions/checkout IS
mirrored and is used normally.

Release payloads become release ATTACHMENTS, outside git history, so ~120 MB
per build never enters a branch. Only the ~500-byte manifest.json is
committed, to the payload-free dist branch, because Forgejo has no
/releases/latest/download/ route (verified 404) for the launcher to poll.
publish-bin.ps1 takes -BaseUrl so the manifest points at the release tag.

Two real gate failures fixed:
- LauncherProjectBoundaryTests asserted four `**` path filters belonging to
  the push triggers that 8be14d39 removed when workflows went manual-only.
  The assertions about what the workflow DOES are untouched.
- MainWindowViewTests failed in Test Case Cleanup with "calling thread cannot
  access this object" while passing in isolation: Avalonia's headless session
  is thread-affine and xUnit ran collections in parallel. Serialized via
  xunit.runner.json, the same settings AcDream.Core.Tests already uses.

Local gate: 12 projects, 14,346 tests, 0 failures.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.Launcher.Tests/AcDream.Launcher.Tests.csproj

@@ -23,4 +23,14 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\AcDream.Launcher\AcDream.Launcher.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <!-- Avalonia's headless session is thread-affine, and its per-test cleanup
+         runs on whichever thread xUnit hands it. Under the default parallel
+         collections MainWindowViewTests failed in Test Case Cleanup with
+         "The calling thread cannot access this object because a different
+         thread owns it" while passing in isolation. Same serialization
+         settings AcDream.Core.Tests already uses. -->
+    <None Update="xunit.runner.json" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
 </Project>

tests/AcDream.Launcher.Tests/LauncherProjectBoundaryTests.cs

@@ -140,10 +140,13 @@ public sealed class LauncherProjectBoundaryTests
             "workflows",
             "headless-portability.yml"));
 
-        Assert.Contains("src/AcDream.Launcher/**", workflow, StringComparison.Ordinal);
-        Assert.Contains("tests/AcDream.Launcher.Tests/**", workflow, StringComparison.Ordinal);
-        Assert.Contains("src/AcDream.Bake/**", workflow, StringComparison.Ordinal);
-        Assert.Contains("tests/AcDream.Bake.Tests/**", workflow, StringComparison.Ordinal);
+        // The four `**` path filters this used to assert belonged to the
+        // push/pull_request triggers that `8be14d39 ci: make GitHub workflows
+        // manual only` deliberately removed; the workflow is workflow_dispatch
+        // now. What this test is actually for — that the portability workflow
+        // BUILDS, TESTS, PUBLISHES and EXECUTES the launcher and bake CLI — is
+        // covered by the content assertions below, which are unaffected by how
+        // the workflow is triggered.
         Assert.Contains("portable-launcher:", workflow, StringComparison.Ordinal);
         Assert.Contains("tests/AcDream.Launcher.Tests/AcDream.Launcher.Tests.csproj", workflow, StringComparison.Ordinal);
         Assert.Contains("tests/AcDream.Bake.Tests/AcDream.Bake.Tests.csproj", workflow, StringComparison.Ordinal);

tests/AcDream.Launcher.Tests/xunit.runner.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "https://xunit.net/schema/current/xunit.runner.schema.json",
+  "parallelizeAssembly": false,
+  "parallelizeTestCollections": false,
+  "maxParallelThreads": 1
+}