fix(ci): restore push triggers for Stainless preview builds

Reverts 859d318 which broke CI by removing push/PR triggers.
Restores automatic workflow runs when code is pushed to preview branches.

Signed-off-by: Charlie Doern <cdoern@redhat.com>

Author: cdoern

.github/workflows/ci.yml

@@ -1,6 +1,17 @@
 name: CI
 on:
- workflow_dispatch:
+  push:
+    branches-ignore:
+      - 'generated'
+      - 'codegen/**'
+      - 'integrated/**'
+      - 'stl-preview-head/**'
+      - 'stl-preview-base/**'
+  pull_request:
+    branches-ignore:
+      - 'stl-preview-head/**'
+      - 'stl-preview-base/**'
+  workflow_dispatch:
 
 jobs:
   lint: