feat(launcher): Gitea-backed alpha update feed replaces the GitHub Releases source

The launcher reported "no client available" because its update source was
pinned to a GitHub Releases manifest in a PRIVATE repo — nothing anonymous
could ever be fetched from it. Switch the feed to the PUBLIC Gitea repo so a
friend needs no account, and add the two commands that publish it.

- ReleaseManifestClient.ProductionManifestUri now points at
  git.snakedesert.se/erik/acdream raw on the `dist` branch. No update
  machinery changed: the existing strict reader already accepts any HTTPS
  manifest, so this is a URL swap plus a build script.

- tools/publish-bin.ps1 publishes the payloads into /bin and writes
  bin/manifest.json (schema v1, SHA-256 + size per artifact):
    client-win-x64.zip    AcDream.App + acdream-headless
    launcher-win-x64.zip  acdream-launcher + co-deployed acdream-bake
  Stamps InformationalVersion ONLY — never -p:Version, which also rewrites
  project-reference versions inside the committed packages.<rid>.lock.json
  files and churned every one of them with a throwaway build stamp.

- tools/publish-dist.ps1 pushes /bin to the Gitea-only `dist` branch from a
  throwaway worktree, leaving the developer's checkout, index, and HEAD
  untouched. It refuses a GitHub remote outright.

Why `dist` and not main: the launcher payload is ~103 MB because the launcher
and its co-deployed bake CLI are each self-contained single files (deliberate,
see AcDream.Launcher.csproj). GitHub hard-rejects files over 100 MB, and all
three refs currently track main, so payloads on main would break every GitHub
push. `dist` is a single-commit orphan branch that each publish REPLACES, so
superseded builds never accumulate. /bin stays gitignored repo-wide and is
force-added only on that branch.

Verified live: manifest and both payloads serve anonymously over HTTPS, and a
downloaded client payload matches its declared SHA-256 and size byte for byte.

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

.gitignore

@@ -2,6 +2,11 @@
 bin/
 obj/
 out/
+# NOTE: the repo-root /bin folder holds the alpha distribution feed written by
+# tools/publish-bin.ps1. It stays IGNORED here on purpose so a stray `git add`
+# can never put ~150 MB of payloads on main (GitHub also hard-rejects any file
+# over 100 MB). tools/publish-dist.ps1 force-adds it onto the Gitea-only `dist`
+# branch instead, which is what the launcher's update feed reads.
 
 # Rider / VS
 .idea/