ci: put the launcher's update pointer in a release, and delete the dist branch

The dist branch existed to carry ~120 MB payloads that could not go on main.
Once payloads became release attachments it held one 500-byte manifest.json,
so it was a whole branch for a reason that no longer applied.

The pointer is now a release asset too: each publish recreates a one-asset
 release naming the versioned build. Forgejo has no
/releases/latest/download/ route (404), so a pointer is still required — but
keeping it in a release means nothing about distribution lives in git: no
payload branch, no bot commits on main, and no push that could retrigger the
pipeline (which is why writing the manifest to main was not the answer either).

Recreating the tag deletes the old release AND its tag; the tag outlives its
release and would otherwise block recreation.

Versioned releases are retained, so older builds stay downloadable.
tools/publish-dist.ps1 is removed — publishing is CI's job now.

tests/AcDream.Launcher.Core.Tests/Updates/ReleaseTransportTests.cs

@@ -91,14 +91,12 @@ public sealed class ReleaseManifestClientTests
 
         Assert.Equal("2.1.0", manifest.Version.Value);
         Assert.Equal(client.LongLength, manifest.RequireClient("win-x64").Size);
-        // Alpha distribution feed: the PUBLIC Gitea repo's `dist` branch
-        // (GitHub stays private, so its Releases feed cannot serve anonymous
-        // friend installs, and its 100 MB per-file limit could not carry the
-        // launcher payload). tools/publish-bin.ps1 writes the payloads and
-        // tools/publish-dist.ps1 pushes that branch — all three must agree on
-        // this URL.
+        // Alpha distribution feed: the manifest asset of the fixed `latest`
+        // release. Nothing about distribution lives in git — the CI release job
+        // republishes this pointer after each versioned release, so it must
+        // agree with this URL.
         Assert.Equal(
-            "https://git.snakedesert.se/erik/acdream/raw/branch/dist/bin/manifest.json",
+            "https://git.snakedesert.se/erik/acdream/releases/download/latest/manifest.json",
             ReleaseManifestClient.ProductionManifestUri.AbsoluteUri);
         Assert.Equal(Uri.UriSchemeHttps, ReleaseManifestClient.ProductionManifestUri.Scheme);
     }