CI: every push builds all targets; main updates a Latest build release

- a newer push to the same branch cancels the run it replaces
- the Latest build pre-release gets every build that worked; a v* tag needs all

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -1,5 +1,7 @@
-# Builds Frame Studio for every computer it runs on, and the Frame Home installer, on each push. Each build is a
-# downloadable artifact of the run; a tag "v*" also publishes them all as a GitHub release.
+# Builds Frame Studio for every computer it runs on, and the Frame Home installer, on every push (any branch or tag),
+# every pull request, and by hand (Actions > build > Run workflow). Each build is a downloadable artifact of the run.
+# A push to main also replaces the "latest" pre-release with them (one place to download the newest of everything);
+# a tag "v*" publishes them as that version's release.
 name: build
 
 on:
@@ -7,6 +9,11 @@ on:
   pull_request:
   workflow_dispatch:
 
+# A newer push to the same branch replaces a run still going (its builds would be out of date anyway).
+concurrency:
+  group: build-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   linux:
     name: Linux ${{ matrix.arch }}
@@ -91,17 +98,28 @@ jobs:
           path: dist/FrameHome-installer.zip
 
   release:
-    if: startsWith(github.ref, 'refs/tags/v')
+    name: Publish
+    # (also when a platform failed: "latest" gets every build that worked; a version release needs them all)
+    if: ${{ !cancelled() && (startsWith(github.ref, 'refs/tags/v') || github.ref == 'refs/heads/main') }}
     needs: [linux, windows, macos, frame-home]
     runs-on: ubuntu-24.04
     permissions:
       contents: write
+    env:
+      GH_TOKEN: ${{ github.token }}
+      REPO: ${{ github.repository }}
     steps:
       - uses: actions/download-artifact@v4
         with:
           path: dist
           merge-multiple: true
-      - name: Publish
-        env:
-          GH_TOKEN: ${{ github.token }}
-        run: gh release create "${{ github.ref_name }}" dist/* --repo "${{ github.repository }}" --title "Frame Studio ${{ github.ref_name }}" --generate-notes
+      - name: Version release (tag v*)
+        if: ${{ startsWith(github.ref, 'refs/tags/v') && !contains(needs.*.result, 'failure') }}
+        run: gh release create "${{ github.ref_name }}" dist/* --repo "$REPO" --title "Frame Studio ${{ github.ref_name }}" --generate-notes
+      - name: Latest build (push to main)
+        if: github.ref == 'refs/heads/main'
+        run: |
+          gh release delete latest --repo "$REPO" --yes --cleanup-tag 2>/dev/null || true
+          gh release create latest dist/* --repo "$REPO" --prerelease --target "${{ github.sha }}" \
+            --title "Latest build (${GITHUB_SHA::7})" \
+            --notes "Built automatically from ${{ github.sha }} on $(date -u '+%Y-%m-%d %H:%M UTC'). Replaced by every push to main."