Move macOS build to a manual-only workflow

Gitea evaluates a job's `if` on the runner, so with no macOS runner the
gated job sat queued forever and kept every run in progress. Make it a
separate workflow_dispatch-only workflow until a macOS runner exists.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.gitea/workflows/macos.yaml

@@ -0,0 +1,24 @@
+name: macos
+
+# A real build. Manual-only for now: there is no macOS runner, and Gitea leaves
+# a job queued (not skipped) when no runner has its label, even behind an `if`.
+# Once an act_runner with the "macos" label is registered, add `push:` here.
+on:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: macos
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check
+        run: scripts/check.sh
+
+      - name: Build (warnings are errors)
+        run: swift build -c release -Xswiftc -warnings-as-errors
+
+      - name: Bundle and ad-hoc sign
+        run: |
+          make bundle
+          plutil -lint dist/Wakeful.app/Contents/Info.plist