CI: build workflows run only from the release branch

Release, FreeBSD and Windows ARM64 builds no longer run on main, PRs or a
schedule; every build job checks for refs/heads/release so a manual run
from another branch is skipped.

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

.github/workflows/freebsd.yml

@@ -1,5 +1,7 @@
 # Builds and tests the workspace on FreeBSD, inside a FreeBSD VM on a Linux runner
 # (GitHub has no FreeBSD runners). GPU tests skip themselves when the VM has no adapter.
+# Builds run only from the `release` branch: release.yml calls this workflow, and a manual run
+# from any other branch is skipped.
 #
 # With `package: true` (release.yml calls it that way, or a manual run) it instead builds the
 # release binaries and uploads `gridcraft-<version>-freebsd-x86_64.tar.gz` as the
@@ -8,15 +10,6 @@
 name: FreeBSD
 
 on:
-  push:
-    branches: [main]
-  pull_request:
-    paths:
-      - Cargo.toml
-      - Cargo.lock
-      - "**/Cargo.toml"
-      - packaging/freebsd/**
-      - .github/workflows/freebsd.yml
   workflow_dispatch:
     inputs:
       package:
@@ -48,6 +41,7 @@ permissions:
 jobs:
   freebsd:
     name: FreeBSD 14 (${{ inputs.package && 'package' || 'build + test' }})
+    if: github.ref == 'refs/heads/release'
     runs-on: ubuntu-latest
     timeout-minutes: 300
     env:

.github/workflows/release.yml

@@ -35,6 +35,8 @@ env:
 jobs:
   version:
     name: version
+    # Only the release branch builds; a manual run from any other branch skips every job.
+    if: github.ref == 'refs/heads/release'
     runs-on: ubuntu-latest
     environment: release
     outputs:

.github/workflows/windows-arm64.yml

@@ -4,19 +4,10 @@
 # out for now: PrintCraft saw an intermittent access violation in egui UI tests there.)
 name: Windows ARM64
 
+# Builds run only from the `release` branch (a manual run from another branch is skipped).
 on:
   push:
-    branches: [main]
-  pull_request:
-    paths:
-      - Cargo.toml
-      - Cargo.lock
-      - "**/Cargo.toml"
-      - "**/build.rs"
-      - .github/workflows/windows-arm64.yml
-      - packaging/windows/**
-  schedule:
-    - cron: "41 4 * * 1" # weekly, so drift in the runner images shows up
+    branches: [release]
   workflow_dispatch:
 
 concurrency:
@@ -33,6 +24,7 @@ env:
 jobs:
   package:
     name: package (cross-compiled on x64)
+    if: github.ref == 'refs/heads/release'
     runs-on: windows-latest
     timeout-minutes: 90
     steps: