Gitea Actions: workflow guards + .gitea release pipeline (#7)

* CI: skip GitHub-specific workflows on Gitea Actions; add workflow_dispatch

Gitea reads .github/workflows/ for compatibility, so without guards it
tries to run the release and wiki-sync workflows on Gitea too - which
fail because they use softprops/action-gh-release@v2 (GitHub-only) and
push to GitHub-hosted wiki URLs.

Add `if: github.server_url == 'https://github.com'` to the
release-builder and wiki-sync jobs so Gitea no-ops them. ci.yml
(plain dotnet build + test) still runs on both, and now also accepts
workflow_dispatch so it can be triggered by hand to verify a self-
hosted runner is picking up jobs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Gitea release workflow: build installer + attach to Gitea release

.gitea/workflows/release.yml runs on the self-hosted Windows runner
when a v* tag is pushed (or via workflow_dispatch with a version
override for testing without bumping the project).

Mirrors the GitHub release workflow shape - dotnet test, choco-install
Inno Setup if missing, run scripts/build-installer.ps1 - then uses
Gitea's REST API directly for the release-creation + asset-upload
steps (Gitea has no equivalent to softprops/action-gh-release). Token
is the runner-injected secrets.GITHUB_TOKEN, which Gitea provides for
GitHub Actions compatibility.

Path location matters: lives under .gitea/ so GitHub Actions never
sees it, while the existing .github/workflows/release.yml stays
GitHub-only (already gated with `if: github.server_url == ...`).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/release.yml

@@ -12,6 +12,9 @@ on:
 
 jobs:
   build-installer:
+    # Gitea reads .github/workflows/ for compatibility, but the create-release
+    # step uses a GitHub-only action. Skip the whole job on non-GitHub runners.
+    if: github.server_url == 'https://github.com'
     runs-on: windows-latest
     permissions:
       contents: write   # needed to create releases / upload assets