ci: reduce launcher PR matrix cost

.github/workflows/main.yml

@@ -4,6 +4,13 @@ on:
   pull_request:
     branches:
       - '**'
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: python-ci-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   run-ci:
@@ -14,8 +21,15 @@ jobs:
 
     strategy:
       matrix:
-        os: [macos-latest, ubuntu-latest]
+        # Pull requests use the three Linux versions plus one representative
+        # macOS lane. Exact main retains the complete two-OS matrix.
+        os: ${{ fromJSON(github.event_name == 'pull_request' && '["ubuntu-latest"]' || '["ubuntu-latest", "macos-latest"]') }}
         python-version: ['3.10', '3.11', '3.12']
+        include:
+          # On pull requests, add the one representative macOS lane. On main
+          # this matches an existing full-matrix entry rather than adding one.
+          - os: macos-latest
+            python-version: '3.12'
 
     steps:
       - name: Checkout code
@@ -25,6 +39,8 @@ jobs:
         uses: actions/setup-python@v7
         with:
           python-version: ${{ matrix.python-version }}
+          cache: pip
+          cache-dependency-path: pyproject.toml
 
       - name: Install dependencies
         run: |

.github/workflows/notify-docs.yml

@@ -2,6 +2,11 @@ name: Notify docs
 on:
   push:
     branches: [main]
+    paths:
+      - README.md
+      - CHANGELOG.md
+  release:
+    types: [published]
 jobs:
   notify:
     runs-on: ubuntu-latest